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ODLIS

Online Dictionary for Library and Information Science

by Joan M. Reitz
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daemon
The Greek word for "guardian spirit." In computing, an auxiliary systems program initiated at startup and executed in the background that performs a specific task when needed, for example, running a scheduler to start another process automatically at a pre-established time, checking incoming e-mail messages for addresses that cannot be found, or notifying the sender that a message could not be delivered. Pronounced "demon."

dagger (†)
In printing, a character in the shape of a vertical stroke crossed above its midpoint, used in text as a second-order reference mark following use of the asterisk (*). When it appears before a personal name in the English language, the dagger indicates that the individual is deceased. Also called an obelisk or long cross. See also: double dagger.

daguerreotype
Historically, the first photographic process that actually worked, producing a positive image directly on a highly polished, silvered copper plate sensitized with iodide vapor. By exposing the plate to light in a camera obscura, a laterally reversed latent image was captured in the photosensitive layer of silver iodide that could be developed with the application of mercury vapor. Made public in 1839, the process was named after its French inventor, the painter of dioramas, Louis Jacques Mande Daguerre, who relied heavily on earlier experiments by Joseph Nicephore Niepce. Daguerre taught the process to Samuel B. Morse (of Morse code) in Paris in 1839, who subsequently taught it to paying students in the United States.

Although the daguerreotype was capable of capturing fine detail, the highly polished surface had a mirror effect when viewed at an oblique angle and was easily scratched and tarnished. For this reason, daguerreotypes were typically protected under a metal mat, covered by a plate of glass, and enclosed in a case (see these examples). Early examples are valued by collectors because each is unique, not having been made from a negative. For other examples, see the online exhibitions Secrets of the Dark Chamber (Smithsonian American Art Museum) and The Dawn of Photography: French Daguerreotypes, 1839-1855 (Metropolitan Museum of Art), or try the Daguerreian Society. Also spelled daguerrotype. Compare with calotype. See also: ambrotype, composite daguerreotype, and tintype.

daily
Issued on a daily basis, with the possible exception of Sundays. Also refers to a serial issued daily, especially a newspaper issued every weekday.

damaged
An item returned to the library in such poor condition that it cannot be placed back on the shelf for circulation, for example, a water-soaked or pet-chewed book. The borrower is normally charged the cost of repair or replacement. New items received from the shipper in damaged condition are returned by the library to the seller for credit or replacement. Click here to see a copy of the first printed edition of Marsilio of Padua's The Defender of Peace damaged in the English bombardment of Copenhagen in 1807 (Royal Library of Denmark). See also: defacement.

dampstain
A visible stain, often in a shade of gray or tan, found on the covers or leaves of a book, caused by exposure to moisture, water, or some other liquid (see this example). When minimal, it is tolerated by collectors in the absence of mildew in very old, scarce books, but its presence lowers the monetary value of the item.

Dana, John Cotton (1856-1929)
A public librarian for over 40 years, John Cotton Dana began his career in 1889 as head of the Denver Public Library, moved to the City Library of Springfield in 1898, and ended his career at the Free Public Library in Newark, New Jersey. An early leader in the library profession, he served as president of the American Library Association (ALA) from 1895 to 1896, as a member of its council from 1896 to 1902, and as president of the Special Libraries Association from 1909 to 1910, an organization he helped to establish. His philosophical approach to librarianship is best expressed in his book Suggestions, published in 1921 by F.W. Faxon. Click here to learn more about John Cotton Dana, courtesy of the Rutgers University Libraries. See also: John Cotton Dana Award.

dance of death
A form of late-medieval literary and visual allegory in which Death, represented by an animated skeleton, leads victims from all walks of life to the grave in a procession or dance (see these examples by Hans Holbein). The images were intended to remind the living of the impermanence of life and the nearness of death. Synonymous with danse macabre and totentanz.

dandy roll
The cylinder that exerts pressure in mechanized papermaking, smoothing the surface and creating designs such as the watermark, countermark, and the lines characteristic of laid and wove paper (see this example).

Dartmouth Medal
A literary award presented annually since 1974 by the Reference and User Services Association (RUSA), a division of the American Library Association (ALA), to the most outstanding reference work published during the preceding calendar year. Click here to see a list of Dartmouth Medal recipients.

dash
A short length of horizontal rule used for punctuation, to separate text, and for decorative effect. In printing, dashes vary in length from the three-em (longest) to the hyphen (shortest). In typing, a dash is made by striking the hyphen key twice in succession (--). In descriptive cataloging, the dash is preceded and followed by a space, but when it is used in subject headings to indicate subdivision, no spaces are included (example: Libraries--Aims and objectives).

dashed-on entry
A pre-AACR2 convention of indicating accompanying material and additional versions on the catalog entry for the main item, a practice that economized on the number of catalog cards needed for items sharing basic bibliographic description. This type of entry was eliminated in AACR2, reflecting a shift from card catalogs to MARC-based electronic catalogs. Synonymous with dash entry and dash on entry.

dasymetric map
A thematic map similar to a choropleth map in the use of areal symbols (tint, shading, hatching, etc.) to represent quantitative data, but instead of mapping the data to areas that correspond to administrative or enumeration units, ancillary variables are employed to change the boundaries of the areas to better represent the areal distribution of classes of data. Click here to see an example showing the distribution of population density in Greece in 1973, courtesy of the Perry-Castañeda Library (to enlarge click on lower right corner of image).

data
The plural of the Latin word datum, meaning "what is given," often used as a singular collective noun. Facts, figures, or instructions presented in a form that can be comprehended, interpreted, and communicated by a human being or processed by a computer. Compare with information and knowledge. See also: data bank, database, data set, and metadata.

data bank
Sometimes used synonymously with database, the term applies more specifically to a collection of nonbibliographic data, usually numeric (example: Child Trends DataBank). Large data banks containing information about individuals (social security numbers, credit history, health records, etc.) have become the subject of controversy as the rapid development of high-speed information technology poses new threats to personal privacy.

database
A large, regularly updated file of digitized information (bibliographic records, abstracts, full-text documents, directory entries, images, statistics, etc.) related to a specific subject or field, consisting of records of uniform format organized for ease and speed of search and retrieval and managed with the aid of database management system (DBMS) software. Content is created by the database producer (for example, the American Psychological Association), which usually publishes a print version (Psychological Abstracts) and leases the content to one or more database vendors (EBSCO, OCLC, etc.) that provide electronic access to the data after it has been converted to machine-readable form (PsycINFO), usually on CD-ROM or online via the Internet, using proprietary search software.

Most databases used in libraries are catalogs, periodical indexes, abstracting services, and full-text reference resources leased annually under licensing agreements that limit access to registered borrowers and library staff. Abbreviated db. Compare with data bank. See also: archival database, bibliographic database, embedded database, metadatabase, and niche database.

database management system (DBMS)
A computer application designed to control the storage, retrieval, security, integrity, and reporting of data in the form of uniform records organized in a large searchable file called a database. The range of available DBMS software extends from simple systems intended for personal computers to highly complex systems designed to run on mainframes.

data compression
The algorithmic re-creation of a data file to reduce the amount of memory required for storage. Exchange of compressed data requires less transmission time but more computation time to restore it to its original form for processing. In digital imaging, a number of compression methods are used, including JPEG, GIF, and LZW. Compression algorithms are classified as lossless or lossy, depending on whether data is lost in compression. Click here to learn more about file compression, courtesy of HowStuffWorks. Synonymous with file compression. See also: compression ratio.

data conversion
The process of translating data from one form to another, usually from human-readable to machine-readable format (or vice versa), from one file type to another, or from one recording medium to another, for example, from film to videotape or videodisc using a telecine.

data dictionary
A set of data descriptions documenting the fields (columns) in the tables of a database system. A data dictionary may describe the data type and other physical characteristics of fields, enumerate allowed values, and specify appropriate usage.

Data Documentation Initiative (DDI)
A project of the social science community to develop a standardized XML markup and representation for codebooks, the primary metadata describing social science data sets. Click here to learn more about the DDI.

data logger
An electronic instrument designed to record measurements (temperature, relative humidity, light intensity, on/off, open/closed, voltage, pressure, etc.) over time. Typically they are small, battery-powered devices equipped with a microprocessor, data storage, and sensor. Most utilize turn-key software installed on a personal computer to initiate the logger and view the collected data. They are used for a wide variety of applications, especially in remote areas for the convenience of automatic recording. Libraries and archives use them to monitor environmental variables that affect the condition of collections.

data mining
The process of using database applications to identify previously undetected patterns and relationships within an existing set of data, for example, common interests among the clientele of a business or other organization.

data processing (DP)
The systematic performance of a single operation or sequence of operations by one or more central processing units on data converted to machine-readable format to achieve the result for which the computer program that controls the processing was written, for example, the compilation of circulation statistics from records of circulation transactions occurring in a library over a given period of time.

data set
A logically meaningful collection or grouping of similar or related data, usually assembled as a matter of record or for research, for example, the American FactFinder Data Sets provided online by the U.S. Census Bureau or the National Elevation Dataset available from the U.S. Geological Survey. Also spelled dataset. See also: social science data set.

data strip
A long, narrow band across the back of a card, coated with a magnetic medium (usually dark in color) bearing encoded digital information that can be read by a specially-designed device (see this example). Commonly used to record the account number on plastic credit and debit cards, data strips are also used on some library cards to record patron ID or card number. Synonymous with magnetic strip, magnetic stripe, and magstripe.

data visualization
The use of electronic tools (software applications) to represent data in the form of charts, maps, tag clouds, animations, or any graphical means to make content easier to understand. Graphic representations of data may reveal hidden patterns and highlight connections among elements not obvious from numerical data. For scholars whose conclusions depend on interpretation of complex statistics, data visualization may facilitate communication to a wider audience. (Adapted from EDUCAUSE.)

date
A particular point in time, usually with reference to a specific event or happening. Date usually means a specific day of the month, but is sometimes given as month and year (e.g., May 1861), or merely the year, as in the publication date of a book or the release date of a motion picture or sound recording. A date range is normally given as the beginning date and ending date, separated by a hyphen (1860-1864), as in inclusive dates and bulk dates. References to increments smaller than a day (hour, minute, second) are typically referred to as time. See also: false date.

date due slip
A card or slip of paper inserted in an item charged from a library collection or a small printed form attached to the inside of the front or back cover or to one of the free endpapers, on which is stamped the date the item is due back in the library (see this example). The paper on which they are printed should be acid-free. Date due slips are sometimes removed by borrowers in an attempt to avoid overdue fines, but the advent of automated circulation systems has nixed this strategy. Synonymous with charge slip. See also: checkout slip.

date line
The line printed at the beginning of a story in a newspaper or article published in a newsmagazine, indicating the date and place of origin of news that is not local. See also: byline.

date range
An interval of time marked by a beginning date and an ending date. Some online catalogs and bibliographic databases allow the user to limit a search to a specific range of publication dates. A year followed by a hyphen (1946- ) limits retrieval to information published in the year specified or any succeeding year, a year preceded by a hyphen ( -1945) limits retrieval to sources published up to and including the year specified, and a year followed by a hyphen and a subsequent year (1939-1945) limits retrieval to sources published in those or any intervening years. See also: bulk dates and inclusive dates.

datum
In cartography, a set of accurately surveyed horizontal control points that define the shape of the earth as an ellipsoid, forming the basis for a two-dimensional system of geographic coordinates, for example, the North American Datum of 1983, a readjustment of a pre-existing horizontal control network established and maintained by the National Geodetic Survey. NAD 83 is composed of over 250,000 monumented control stations across the continental United States, interconnected by survey observations. The stations are used by surveyors operating at the federal, state, county, and city levels to reference boundaries, provide control in mapping and charting, and for other purposes. Sea level is the vertical datum used to calculate elevation, but because the level of the sea surface is determined by gravity (and the earth's rotation), which varies according to differences in the density of the earth's core, sea surface topography varies significantly. To assure accuracy, geographers have developed sophisticated techniques for measuring mean sea level. To learn more, see Peter H. Dana's Geodetic Datum Overview. Plural: datums.

In a more general sense, any numeric value or geometric surface, line, or point that serves as a base or reference for other quantities (SARBC Map and Compass Glossary). In the broadest sense, a thing that is given or known to be factual, upon which a reasoned argument or calculation is based. Also, an assumption or premiss from which inferences are subsequently made (OED).

daybook
In bookkeeping, a record of the details of each day's receipts and expenditures in chronological order of occurrence (usually entered in a bound volume), as distinct from a ledger in which financial transactions are recorded by account, as credits and debits. Click here to see a 19th-century medical example (University of Virginia Health Sciences Library) and here to see an example kept by an artist. Also spelled day book. Synonymous with waste book.

Also, a calendar, in print or electronic format, of forthcoming events (celebrations, performances, meetings, workshops, seminars, etc.). Also used in reference to a calendar designed as a personal organizer. Click here to see the daybook of President John F. Kennedy's personal secretary, Evelyn Lincoln (JFK Presidential Library & Museum).

dB
See: decibel.

deaccession
The process of deleting from an accession record documents and other materials that are to be removed from a library collection. Also refers to any item so removed. The opposite of accession.

In archives, the process of removing records or documents from official custody, undertaken after careful consideration, usually as the result of a decision to transfer the material to another custodian or because the legal owner desires its return or the material is found upon reappraisal to be of doubtful authenticity or inappropriate for the collection. Synonymous with permanent withdrawal.

deacidification
A general term for a variety of costly preservation processes that chemically reduce the acid content of paper documents to a pH of 7.0 (neutral) or higher, usually undertaken at a professional conservation center to prevent further deterioration. An alkaline buffer may be deposited in the process of deacidification to neutralize any acids that may develop in the future. Brittleness is not reversed by deacidification.

In aqueous deacidification, water is used as the solvent carrier of the alkaline agent; in nonaqueous deacidification, organic solvents are used as the carrier. In vapor phase deacidification, documents and the pages of volumes are interleaved with treated sheets that emit an alkaline vapor, a method now rarely used because it produces toxic vapors and does not leave an alkaline reserve (Richard Pearce-Moses, A Glossary of Archival and Records Terminology). Mass deacidification is the shipment of a quantity of documents to a central location for processing, usually in small batches rather than individually. Click here to see mass deacidification at the Zentrum f�r Bucherhaltung in Leipzig, Germany.

Dead Sea Scrolls
Ancient papyrus and parchment manuscripts stored inside large pottery jars, discovered in caves in the Judean Desert in 1947 by Bedouin shepherds. Radiocarbon dating has established that the scrolls, and the Essene community at wadi Quram with which they are believed to be associated, date from 250 B.C. to A.D. 65. Written in Aramaic, the scrolls comprise about 800 documents of which most are in fragmentary condition. They include the oldest extant text of the Old Testament. The tedious work of piecing them together has taken decades. The scrolls are in the possession of the Israel Antiquities Authority in Jerusalem, where they are being prepared for publication by Oxford University Press in what will eventually be a thirty-five volume work entitled Discoveries in the Judaean Desert (see Dead Sea Scrolls Foundation). The Library of Congress provides the online exhibit Scrolls from the Dead Sea. Examples can also be seen in the Schøyen Collection (Oslo and London) and Treasures from the World's Great Libraries, courtesy of the Israel Antiquities Authority and the National Library of Australia.

dealer
An individual or commercial company in the business of buying and selling new and used books to libraries, collectors, and other booksellers. Although the term is sometimes used synonymously with vendor or jobber, it is usually reserved for specialists who deal in out of print titles, rare books, periodical back issues, etc. See also: antiquarian bookseller.

dean
The position title used in some institutions for the chief executive of a large academic library system in which the professional staff have faculty status and the chief executive also serves as head of the library faculty. The official title is usually "Dean of Library Services" or "Dean of Information Services." Compare in this sense with library director. Also, the title designating the chief academic and administrative officer of most library and information studies programs in the United States. A dean normally serves at the discretion of the president of the institution.

debossed
A title (or other text) or a design or image, such as a logo, heat-pressed into the surface of paper by means of a die, creating depressions or indentations in the surface rather than the raised impressions made in embossing. The same techniques used in embossing (blind, ink, and foil) can be used in debossing to create texture and visual effects. Debossing is also done on hard and soft book covers (see this example of blind debossing). (Adapted from About.com)

decal
An image (often a logo) made on paper specially treated to allow the image to be transferred to another surface, such as glass, plastic, or metal, usually by wetting the paper, then placing it face down against the other surface and peeling away the backing sheet. In libraries, decals are collected as a form of ephemera.

decennial
Issued every 10 years (example: U.S. Census). Also refers to a serial publication issued every 10 years. See also: annual, biennial, triennial, quadrennial, quinquennial, sexennial, and septennial.

decibel (dB)
A standard logarithmic unit used to measure level of sound pressure (loudness). One decibel is equal to one-tenth of a unit of sound measurement known as a bel. Developed from methods used during the 1920s at Bell Laboratories to quantify reductions in audio levels in telephone circuits, the dB scale ranges from 0dB at the threshold of human hearing to 140dB, the threshold of auditory pain (see this Decibel Comparison Chart).

decimal point
The period used in the numeric portion of Library of Congress Classification notation (example: DK 265.9) and following the third digit of a class number in Dewey Decimal Classification (947.084) to indicate that succeeding digits are to be treated as a decimal fraction.

Decision Document
The official document sent to the dean of a library and information studies program and to the institution�s chief executive officer conveying the accreditation action taken by the Committee on Accreditation (COA) of the American Library Association (ALA) as the result of a two-year comprehensive review to verify that the program conforms to the ALA's Standards for Accreditation of Master's Programs in Library and Information Studies (2008). If accreditation is withdrawn or denied, the program or institution may appeal the decision. See also: special report.

deckle edges
The uneven or feathered edge of a sheet of handmade paper, created by the flow of liquefied fibrous stock between the frame (deckle) and sieve of the mould used in manufacture. The same effect is achieved in machine-made paper by exposing the edge to a jet of air or water. In quality bookbinding, deckle edges are considered tasteful, but since books tend to collect dust when stored on an open shelf, and rough edges are difficult to clean, the feature is not practical. Click here to see an example and here to compare deckle edges with other edge treatments. Compare with cut edges.

declassified
A document no longer protected against unauthorized disclosure because the security classification assigned to maintain confidentiality has been officially changed or canceled. Examples can be seen at the Web site maintained by The National Security Archive, an independent non-governmental research institute and library located at George Washington University in Washington, D.C. The opposite of classified. See also: declassification.

declassification
The process of removing the security classification from materials restricted by a government for reasons of national security, to make the information contained in them accessible to individuals without security clearance. In a declassification project, an entire category or group of documents is evaluated for possible declassification (see this example at the Gerald R. Ford Presidential Library and this project at the U.S. Department of State). Compare with downgrade. See also: reclassification.

declination
Angular distance north or south from the celestial equator measured on a great circle (meridian) passing through the celestial poles, corresponding to terrestrial latitude. Magnetic declination (sometimes called magnetic variation or compass variation) is the angle between magnetic (compass) north, determined by the earth's magnetic field, and true north for a given location. The actual location of the magnetic north pole changes over time due to shifts in the earth's magnetic field, but its current location is northwest of Hudson's Bay in northern Canada, about 450 miles from the geographic north pole. The line of zero declination runs from magnetic north through Lake Superior and the western panhandle of Florida. Along this line, true north is the same as magnetic north. Magnetic declination is designated positive when the angle measured is east of true north and negative when west of true north. The orientation of maps and charts is based on geographic north because it remains constant. On some maps, a declination diagram or note, usually located near the scale, indicates the angular relationships of true north, magnetic north, and grid north (see this example). Click here to see the concept illustrated and here to learn more about declination, courtesy of Wikipedia.

decomposition vent
An opening in a storage chamber made to allow the escape of gases (usually toxic or flammable) produced in the deterioration of the stored material. For example, the National Fire Protection Association (NFPA) has established a standard requirement for decomposition vents in chambers used to store chemically unstable cellulose nitrate film.

decorated initial
An initial letter in an illuminated manuscript or early printed book embellished in an abstract, nonrepresentational style, rather than with foliate, zoomorphic, and/or anthropomorphic motifs or pictorial elements. Click here to see a fine penwork example in a 15th-century Spanish antiphonal (Dartmouth College Library, MS 002103) and here see a large painted example in a 14th-century Italian Bible (Cary Collection, Rochester Institute). Within a medieval manuscript, there is usually a hierarchy of initials of varying size and complexity to designate the beginning of sections, chapters, paragraphs, and other breaks in the text (see this example, courtesy of the British Library, Arundel 155).

decorated map
An old map embellished with purely ornamental motifs (foliage, geometric designs, etc.) or drawings of human figures, animals, or small landscapes that may be related to the map's content, but are not used to represent data. A coat of arms signified land ownership. Map decoration usually appears around the edges, in the corners, over the oceans, or in the form of an elaborate cartouche. Click here to see a heavily decorated 17th-century world map and here to see an 18th-century example depicting the Salzburg province of Austria (Library of Congress) and here for an elaborate 19th-century French example (George Glazer Gallery). Click here to see a 20th-century manuscript chart of the Far East with decoration superimposed on the mapped area (National Maritime Museum). Compare with illustrated map and pictorial map.

decorated paper
Fine paper hand-printed in Germany, France, and Italy from patterns carved into woodblocks, used in luxury bookbinding from the 18th century on for doublures and flyleaves. Dutch gilt was a multicolored floral pattern blocked in gold, shipped from Germany to the Netherlands for re-export. Click here to see a sample of brocade paper made in the 18th-century (Koninklijke Bibliotheek) and here to see decorated paper used as doublure and flyleaf in a 19th-century deluxe binding (University of North Texas Libraries). To see examples of decorated paper used as a covering material, try a keywords search on the term in the British Library's Database of Bookbindings. Click here to see a late 19th-century German recipe book for making decorated paper (Koninklijke Bibliotheek) and here to see a collection of decorated papers at the Folger Shakespeare Library. See also: marbling, paste paper binding, and silhouette paper.

decretals
A book containing a collection of letters written to transmit papal decrees, usually concerning canon law, often made in response to a specific appeal. Michelle Brown notes in Understanding Illuminated Manuscripts (Getty Museum/British Library, 1994) that copies of decretals used by ecclesiastical and civil officials, and for purposes of study at universities, often included commentaries written as glosses alongside the text and sometimes decoration (miniatures, bas-de-page scenes, grotesques, etc.). Click here to view an illuminated copy of the decretals of Pope Gregory IX (Bodleian Library, University of Oxford, MS Lat. th.b.4), and here to page through decretals compiled by Gratian in the 12th century (Getty Museum, MS Ludwig XIV 2).

dedicated
In computing and communications, a device or channel reserved for a specific use. In libraries, dedicated servers are used to run the online catalog and to provide access to the library's Web site. See also: dedicated line.

dedicated line
A direct pathway to the Internet or some other computer network via a separate telecommunications channel not shared with multiple users as in dial-up access but available around the clock to a specific user or group of users for a designated purpose. When accessed through a common carrier, the channel is called a leased line.

dedication
A brief note in which the creator of a work addresses it to one or more persons, usually a colleague, mentor, or family member, as a sign of honor, appreciation, or affection. In books, the author's dedication appears in the front matter, usually printed on the recto of the leaf following the title page. Click here to see the handwritten dedication by 17th-century composer Michael Praetorius of his motets to Christian IV of Denmark (Royal Library of Denmark) and here to see the dedication by William Davenant of a printed edition of his play The Just Italian to the Earl of Dorset (Columbia Rare Book & Manuscript Library). Compare with acknowledgments.

dedication copy
A copy of a book or other work inscribed by the author, editor, or illustrator to the person or persons to whom the work is dedicated. In the antiquarian book trade, a dedication copy may be of substantially greater value than a copy with no inscription and is considered one of the most collectible presentation copies of an edition. Click here to see the hand-colored copy of Le Jardin de Plaisance & Fleur de Rhetorique, an anthology of poems edited by Anthoine Vérard, dedicated to the French King in about 1500 (Royal Library of Denmark).

deduping
Removal of all but one occurrence of a bibliographic record from a file of machine-readable records, one of the initial steps in processing a MARC database. Deduping is a batch process that prevents confusion in the minds of users, conserves computer storage, and allows reliable usage statistics to be collected. Duplicate records are not uncommon because the "cancel holdings" command in OCLC software does not delete a record from the library's OCLC tapes. Synonymous with duplicate removal and duplicate resolution.

deed
A legal document, written or printed, stating a contract, agreement, or transfer of property, especially real property, usually signed by the parties. As a legal instrument, deed is distinguished from title, which is a legal right. Although title is sometimes used synonymously with deed, the latter is normally used only in the narrower sense of the actual instrument. Click here to see a 16th-century English title deed written on parchment and here to see an 18th-century American example signed by Daniel Boone, courtesy of The Lilly Library at Indiana University. The Australian Memory of the World Register provides an image of the Deed of Settlement of the South Australian Company (1856). See also: charter.

deed of gift
A signed document stating the terms of agreement under which legal title to real, personal, or intellectual property, such as a gift of materials to a library or archives, is transferred, voluntarily and without recompense, by the donor to the recipient institution, with or without conditions specifying access, use, preservation, etc. (see the deed of gift for the Statue of Liberty [1884] courtesy of NARA).

deep linking
A link made from a Web document to the interior of another Web site, bypassing the second site's homepage, usually without any indication that a shortcut has been taken. Deep linking raises digital rights issues, particularly for commercial entities that derive income from advertising on their main page. Likelihood of litigation depends on the type of site involved and the nature of the content accessed. Libraries should seek permission before deep linking from their Web pages.

deep web
Publicly accessible information available via the World Wide Web but not retrievable using search engines that rely on crawlers or spiders, for example, data in file formats such as PDF, database content accessible only by query, information contained in frames, etc. The number of documents available in the deep web is estimated to be 400-500 times greater than the amount of content retrievable via conventional search engines (the "surface Web"), with over half of the "hidden" content residing in topic-specific searchable databases. CompletePlanet is an example of Internet services specifically designed to provide access to information buried deep in the Web. See also OAIster and Wikipedia. Synonymous with invisible web.

The term is also used for password-protected Web content available only to authorized users (members, subscribers, etc.).

deerskin
A soft leather made from the skin of a deer. Its use in bookbinding is rare (see this example, courtesy of Washington State University). On medieval bindings, it was sometimes applied as an outer layer to protect the inner covering material. Click here to see a 14th-century example (Koninklijke Bibliotheek).

defacement
Damage to library materials by deliberate intent, rather than accident or neglect, including but not limited to cutting or tearing of pages and covers, underlining or highlighting portions of text, and writing or doodling in margins. Compare with vandalism.

de facto standard
A criterion or consistent manner of doing something, so established in practice that adherence is widespread if not universal, although its status has never been formalized. Such standards are often the result of one method or product becoming so dominant in the market place that its influence is comparable to that of a formally established standard. Examples include the Kermit communication protocol in computing and the compact cassette in sound recording. Compare with de jure standard. See also: best practices.

defamatory
Words that are damaging to a person's reputation or character. See also: libel.

default
A value, option, or setting automatically selected in a hardware or software system in the absence of specific instructions from the user. The default setting may be displayed on the data entry screen to allow the user to see what action will be taken if no input is provided.

definition
One meaning of a word expressed clearly and concisely. Because some words have more than one meaning, a word may have more than one definition. In lexicography, a word or phrase is defined by first specifying the class (genus) to which its referent belongs, then indicating the characteristics that distinguish the referent from others of the same class. Definitions are provided in dictionaries and glossaries and are also included in some concordances and thesauri. In most dictionaries, the modern definition of a word is given first and the oldest last, but there are notable exceptions to this rule. Abbreviated def. See also: headword.

Also refers to the distinctness of a printed or photographic image.

definitive edition
An edition of the complete text of an author's work or works, usually edited and published after the individual's death in a form considered final and authoritative, often including the critical apparatus documenting variations in the work and explaining the editor's choice of version. Also refers to the text of an anonymous work considered by scholars or other experts, upon close examination, to be closest to the original version. Compare with authorized edition. See also: critical edition and variant edition.

definitive work
The work which is generally considered to be the best and most complete treatment of a subject, for example, the definitive biography of a notable person. Subsequent works on the same subject may alter such an assessment. Compare with definitive edition.

degaussing
The process of permanently removing data recorded on a magnetic medium (hard disk, floppy disk, magnetic tape, etc.) by neutralizing the magnetic signals in which the information is encoded, accomplished by subjecting the medium to a magnetic field generated by a device called a degausser, named after the German scientist Carl Friedrich Gauss, who contributed significantly to many fields in mathematics and science, including magnetism. Click here to learn more about degaussing, courtesy of Wikipedia. Synonymous with erasure.

degradation
A loss of image or signal quality, usually in the process of reproduction or transmission.

degressive bibliography
A term introduced by Bodleian librarian Falconer Madan in the early 20th century for his habit of varying the amount of detail in the bibliographic description of a work based on the period of time in which the work was published or on the importance of the publication. Under this principle, the first edition of a work might merit more detailed description than a subsequent edition or reprinting.

de jure standard
A criterion or consistent manner of doing something, formally established in a deliberative process involving one or more professional organizations or industry groups, a government body, or a recognized standard-setting organization (see International Organization for Standardization). It is not unusual for the development process to require negotiations in which a consensus is reached among parties with competing interests, especially when the financial stakes are high. Compliance is not compulsory, but may be made so by national regulations. The Z39.50 client-server protocol and Ethernet are examples of de jure standards. Compare with de facto standard.

delamination
The process of removing layers of thin, clear plastic film from a sheet previously subjected to the process of lamination. Because laminate adheres to the surface to which it is applied, delamination often causes irreversible damage to the laminated document. For this reason, encapsulation is preferred by preservationists.

Also refers to the process by which the components of a sheet of writing or binding material composed of multiple layers adhered one to another come apart, usually from heavy use, as in a sheet or roll of papyrus (see this example, courtesy of the Schøyen Collection, MS 1644). In nonprint media composed of multiple layers (compact discs, DVDs, photographic film, magnetic tape, etc.), delamination occurs when the binding mechanism fails.

delayed publication
A book or periodical not issued on schedule, usually due to delays in production. Also refers to new information not published in a timely manner, for whatever reason.

delete
To remove, erase, or omit a character, word, or passage from a text or document. In computing, to erase a character, word, passage, or entire file from memory, usually by pressing the "Backspace" key on a keyboard or by highlighting text and pressing the "Delete" key or selecting the "Delete" option from a menu or toolbar. Most software systems allow the user to "Undo" a deletion while the application remains open.

delimiter
In a general sense, any character or sequence of characters used in an electronic database to separate discrete elements of data within a field (or fields) of a record. In the MARC record, a character used as the first character of a two-character subfield code to indicate the beginning of a subfield, separating one data element from another within the field. The display representation of the MARC subfield delimiter is not standardized. In OCLC it is represented by a double dagger (‡) and in Library of Congress cataloging by the dollar sign ($).

delinquent borrower
A borrower who fails to return items charged from the library collection within the allowed time or who fails to pay fines or for lost items. Most libraries impose sanctions on borrowers who do not meet their obligations. Such a person may be barred from checking out additional materials. Public libraries may eventually send the borrower's account to a collection agency. Some academic institutions withhold the diploma until library fines are paid. Compare with problem patron.

delivered price
A price for merchandise which includes shipping and handling (packing).

delivery time
The amount of time it takes to receive materials ordered from a vendor, usually 1-3 months. Delivery time varies with type of material, amount of information provided by the library, and specific vendor. From book jobbers that maintain adequate inventories, libraries can expect receipt of an initial shipment containing 75-80 percent of materials ordered within 2 weeks of date of order. Vendors used by academic libraries typically deliver within 6-8 weeks. As a general rule, materials recently published by major houses are delivered faster than older publications issued by smaller companies. Titles published abroad may take longer because international shipping requires more time than domestic shipping. A service charge is usually added for a rush order. Some vendors automatically cancel orders that remain unfilled after 6 months, but others leave them open indefinitely or expect the library to specify the action to be taken. See also: claim.

deluxe binding
French for "of elegance." A binding of very fine quality, usually covered in leather or fine cloth stamped or tooled in gold, sometimes with gilt edges and doublures or endpapers of marbled or decorated paper. Click here and here to see examples by 16th-century Saxon binders (Dresden: Treasures from the Saxon State Library) and here to see an 18th-century example in morocco by the First Stadholders' Bindery in The Hague (Koninklijke Bibliotheek) Click here to see the inside of a 19th-century French deluxe binding with tooled leather doublures and marbled endpapers (Princeton University Library). Also spelled de luxe binding. Compare with fine binding. See also: deluxe edition.

deluxe edition
An edition printed on better quality paper than the standard trade edition, sometimes from specially cast type, usually bound in leather or some other material of fine quality (see this example). Deluxe editions may also be larger in size, more lavishly illustrated, and published in limited edition. Also spelled de luxe edition. Synonymous with fine edition and luxury edition. See also: deluxe binding.

demand
The number of people who need or request a product or service. In libraries, high-demand items may be ordered in multiple copies or placed on reserve to ensure access. In public libraries, low-demand items in the circulating collection may be candidates for weeding. Demand for library services usually peaks at different times during the day, week, month, and year. Transaction logs can be helpful in tracking and anticipating patterns of usage.

DEMCO
A commercial company that provides furniture, equipment, and supplies for the library, school, office, and home. DEMCO also provides periodical subscription services. Click here to connect to the DEMCO homepage. See also: Brodart, Gaylord, and Highsmith.

demographics
A statistical profile of the characteristics of a community or other population, usually including age, education, income, and ethnic background, useful in tailoring services to suit clientele and in planning marketing campaigns.

demolding
The process of removing mold and mold spores from a book or library collection to prevent an infestation from spreading (heavily infested items should be discarded whenever possible). When done professionally, affected materials are first desiccant air dried to remove excess moisture, then treated with antimicrobial cleaning solutions and sanitizers supplied by companies such as Microban. Mold in library carpet and furniture can be eliminated by using a fungicidal disinfectant. On hard surfaces, such as shelving, a mild bleach solution can be used as a wipe-down agent. For more information, see the Oxford University Library's guidelines on Collection Care & Conservation. Also spelled demoulding.

demonstration recording
A recording on audiotape or compact disc of a tune or several tunes, intended to showcase a songwriter's or artist's talents and abilities to agents, producers, music publishers, record labels, record clubs, etc., or as sketches to share with fellow musicians. Made for reference purposes, not commercial release, and seldom heard by the public, demos are typically recorded on comparatively crude equipment, such as "boom box" cassette recorders, small four-track or eight-track machines, or personal computers.

density
In typography, the number of characters filling a given space, a variable affecting legibility of type. In photography, the degree of opacity of a developed photosensitive medium, such as film. In printing and photography, the density of an image is measured by an instrument called a densitometer.

In computing, the amount of data, usually measured in bits or bytes, that can be stored in or on a given storage medium, such as a memory chip or portable disk. A floppy disk can be single-density, double-density, high-density, or extra-high-density. A disk drive designed to support the specific density level is required.

In photography, the relative difference between the lightest and darkest portions of the image, as measured by an instrument called a densitometer. Also, the relative amount (opacity) of the material forming the image on exposed photographic film (usually silver oxide) which affects the amount of light transmitted through the negative.

dentelle binding
A style of 18th-century leather binding in which the covers are decorated on the outer and/or inner surface with broad, full borders gold-tooled in a finely detailed pattern resembling lacework. Click here to view a blankbook gold-tooled in dentelle style (Koninklijke Bibliotheek) and here to see dentelle decoration of the turn-ins on a deluxe binding (University of Pittsburgh Libraries). To see more examples, try a keyword search on the term in the British Library's Database of Bookbindings.

departmental library
A type of academic library that serves the information and research needs of the faculty members of a department within an institution of higher learning, usually a large university. Departmental libraries are also used by students enrolled in courses in the discipline(s) taught by the department, especially graduate students. If acquisitions are funded through the department, selection is usually the responsibility of the teaching faculty in collaboration with the departmental librarian.

dependent work
In library cataloging, a work that is contingent in some way on a previously published work by another author. The category includes abridgments, arrangements, commentaries, continuations, dramatizations, sequels, revised editions, and supplements. Synonymous with related work. Compare with derivative work.

deposit
Any addition to archival holdings, usually a transfer of materials from some other location or agency, but the term also applies to materials on loan for a period of fixed or indefinite duration. The depositor usually retains legal ownership and responsibility, except in the case of gifts. See also: deposit copy and depository library.

Also refers to a fixed fee deposited in the account of a person who is not a member of the library�s regular clientele but who wishes to receive borrowing privileges, usually refundable upon return of the borrowed materials or when the borrower wishes to terminate the agreement. Not all libraries have such a policy.

Also, the legal requirement that one copy of any unpublished work accompany an application for copyright registration. In the United States, two deposit copies of the best edition of a published work are required for copyright registration. Click here to learn more about the deposit requirements of the U.S. Copyright Office.

deposit account
In acquisitions, a vendor prepayment account into which the customer deposits a substantial sum, against which orders are subsequently charged. When the balance in the account reaches zero, an additional amount must be deposited for fulfillment to continue. In return, the library receives a financial incentive in the form of an annual credit based on an agreed rate, a larger than normal discount on purchases, or interest paid on the balance in the account. A library's funding authority usually dictates the feasibility of this type of account (some institutions prefer to earn interest on the money rather than allow the library to expand its purchasing power). There is risk to the customer, should the vendor go out of business before the end of the deposit period.

deposit copy
A copy of a new publication sent without charge to a copyright depository or other designated library by the author or publisher in compliance with national copyright law. In the United States, the deposit copy is sent with the completed copyright application form and copyright fee to the U.S. Copyright Office of the Library of Congress in Washington, D.C. Synonymous with statutory copy.

deposition
Out-of-court testimony given under oath, often in an attorney's office, by the defendant or plaintiff, a witness to the event, or an expert witness, and transcribed by a court reporter for use in pretrial discovery (investigation) or in court, as though the witness were present and testifying (see this historic example). If a written transcript is requested, the deponent normally receives a copy. Depositions are increasingly recorded on videotape. At trial, deposition testimony may be used to impeach a witness who makes contradictory statements or to refresh the memory of a witness. If a deposed witness is unavailable at time of trial (for example, in a case of serious illness or death), the deposition may be read to the jury in place of in-person testimony. Also refers to the process of taking such testimony.

deposit library
A national library to which a publisher is required by law to give at least one copy of each book it publishes. In the United States, the deposit library is the Library of Congress in Washington D.C.

depository library
A library legally designated to receive without charge all or a portion of the government documents provided by the U.S. Government Printing Office (GPO) and other federal agencies to the Superintendent of Documents for distribution through the Federal Depository Library Program (FDLP), having made a legal commitment to comply with federal regulations concerning maintenance and accessibility. Some federal depositories also collect publications issued by state government agencies. A regional depository library receives and retains permanently at least one copy of all the documents distributed through the FDLP, but a selective depository library receives only a percentage of the available publications and is required to retain them for a minimum of 5 years. Depository libraries are required to complete a self-study and/or undergo inspection at intervals of 6-7 years to assure compliance with FDLP rules and regulations. Click here to connect to the Federal Depository Library Directory. Compare with repository. See also: basic collection, Depository Library Council, and depository library number.

Depository Library Council (DLC)
Formally established in 1972, the Depository Library Council is appointed by the Public Printer to advise on matters pertaining to the Federal Depository Library Program (FDLP) as provided in Title 44 U.S.C. The mission of the DLC is to assist the U.S. Government Printing Office (GPO) in identifying and evaluating alternatives for improving public access to government information through the FDLP and for optimizing available resources. Its 15 members are selected to provide a diverse range of opinion and expertise, and to represent a cross section of the various types of DLP libraries, with at least half of the members employed in depository libraries in positions that provide experience in a documents department. Click here to learn more about the DLC.

depository library number
The unique identification number assigned by the U.S. Government Printing Office (GPO) to each depository library in the Federal Depository Library Program (FDLP), consisting of four digits (example: 0063) or four digits plus an alphabetic character (0063B), used to record the library's selections and to distribute materials. The number can also be used to view an online list of the item numbers selected for receipt by the library (see the Item Lister). The depository library number is included at the beginning of each entry in the online directory of depository libraries available via GPO Acccess (click here to connect). Synonymous with depository number.

depth
The thickness of a bound volume at its thickest point (usually the spine) with the covers included. Average depth determines how many volumes will fit on a shelf of given length. Also refers to the width of a bookshelf from front to back. Most library shelving is 8, 9, 10, or 12 inches deep. See also: height.

In indexing, a combination of the average number of index terms (subject headings or descriptors) assigned to documents indexed and the specificity of the terms used (ASIS Thesaurus of Information Science and Librarianship, Information Today, 1998).

depth indexing
An indexing system that attempts to extract all the concepts covered in a work, including any subtopics, as opposed to summarization, in which a work is indexed only under its dominant subject. Library catalogers have traditionally looked for the single concept that best describes the entire content of an item, leaving depth indexing to commercial services that index parts of items (articles in periodicals, book chapters, essays in collections, etc.).

derivative indexing
A method of indexing in which a human indexer or computer extracts from the title and/or text of a document one or more words or phrases to represent subject(s) of the work, for use as headings under which entries are made. Synonymous with derived indexing and extractive indexing. Compare with assignment indexing. See also: automatic indexing and machine-aided indexing.

derivative work
A work based on one or more preexisting intellectual or creative works, which transforms the content of the original(s) in a significant way. Examples include abridgments, adaptations, musical arrangements, revisions, translations, compilations, etc.). Under U.S. copyright law, the rights to produce derivative works are retained by the copyright holder. Compare with dependent work.

descender
In typography and calligraphy, the stroke of a lowercase letter that extends below the lowest point of an x-height letter (a, c, e, m, etc.). The letters of the roman alphabet that have descenders are: g, j, p, q, and y. The descender line is an imaginary horizontal line connecting the bottoms of descender letters, not to be confused with the base line. Compare with ascender. See also: primary letter.

Describing Archives: A Content Standard (DACS)
Produced by the Canadian-U.S. Task Force on Archival Description (CUSTARD) and funded by the National Endowment for the Humanities (NEH), DACS is a content standard for creating access tools for archival materials, published in 2004 by the Society of American Archivists (SAA). It supersedes Archives, Personal Papers, and Manuscripts (APPM) published by the SAA in 1989. Applicable to all types of archival materials at all levels of description, DACS can be used for any type of descriptive output, including the two most widely used standards, MARC 21 and Encoded Archival Description (EAD). Divided into three parts ("Describing Archival Materials," "Describing Creators," and "Forms of Names"), DACS also includes a glossary, a list of companion standards, and crosswalks to APPM, ISAD(G), ISAAR(CPF), MARC 21, and EAD.

descriptive bibliography
The close study and description of the physical and bibliographic characteristics of books and other materials, including detailed information about author, title, publication history, format, pagination, illustration, printing, binding, appearance, etc., as opposed to an examination of content. Also refers to a work that is the result of such study. Descriptive bibliography is considered a branch of analytical bibliography.

descriptive cataloging
The part of the library cataloging process concerned with identifying and describing the physical and bibliographic characteristics of the item, and with determining the name(s) and title(s) to be used as access points in the catalog, but not with the assignment of subject headings and genre/form terms. In the United States, Great Britain, and Canada, descriptive cataloging is governed by Anglo-American Cataloguing Rules (AACR2). See also: authority control and subject analysis.

descriptive metadata
Data about an information resource that is intended to facilitate its discovery, identification, and selection. Descriptive metadata is also used to bring together all the versions of a work in a process called collocation, and for acquisition purposes. When viewed as metadata, traditional library cataloging is descriptive, as are such schemes as the Dublin Core Metadata Element Set and the VRA (Visual Resources Association) Core. Descriptive metadata is also used for evaluation, both narrative (reviews, etc.) and formal (content ratings); for linkage (relationships between a resource and other things); and for usability. Compare with administrative metadata and structural metadata.

descriptor
In indexing, a preferred term, notation, or sequence of symbols assigned as an access point in the bibliographic record representing a document to indicate one of the subjects of its text (synonymous in library cataloging with the term subject heading). In bibliographic databases, descriptors appear in the DE or SUBJECT field of the record. Major descriptors are distinguished from minor descriptors by a special character, usually the asterisk. Some abstracting and indexing services, such as ERIC and Psychological Abstracts, provide a list of authorized indexing terms in the form of a printed or online thesaurus. Compare with identifier. See also: aboutness, controlled vocabulary, and descriptor group.

descriptor group
In some indexing systems, preferred terms are grouped in broad subject categories that together serve as a "table of contents" to the controlled vocabulary. The group to which a specific descriptor is assigned is usually indicated by a code in the entry for the term in the thesaurus of indexing terms; for example, the group code GC: 730 in the entry for the term "Literature Reviews" in the Thesaurus of ERIC Descriptors indicates that it is assigned to the descriptor group "Publication/Document Types."

deselection
In serials, the process of identifying subscriptions for cancellation, usually in response to subscription price increases and budgetary constraints. In book and nonprint collections, the process of identifying titles for weeding, usually on the basis of currency, usage, and condition. The opposite of selection.

deselections
Item numbers previously selected by a depository library under the Federal Depository Library Program (FDLP), which it no longer chooses to receive. Deselections can be made at any time in the GPO online database by using the depository library number and a unique password assigned to the library (click here to see the appropriate screen on the FDLP Desktop). Confirmations are sent via e-mail. Amendments appear within two weeks in the Item Lister.

desensitization
The process of deactivating the magnetic strip affixed to a book or other printed item to prevent the security alarm from sounding when the borrower exits the library, a step performed by circulation staff when the item is checked out, using a device called a desensitizer. A different device is required to desensitize magnetic media (audiocassettes, videocassettes, etc.).

desiccant
A drying agent such as silica gel used in museums and libraries to remove water vapor from a small enclosed space when control of relative humidity is an important factor in the preservation of specimens, documents, and other materials in storage or on exhibit. Because desiccants release moisture when heated, they can usually be reused. See also: molecular sieve.

desiderata
A list of books and other materials needed and wanted by a library or archives, to be purchased when budget permits or as cash donations are received. Synonymous in this sense with waiting list and want list. Also refers to a list of subjects or topics on which a writer or researcher requires information.

design drawing
A technical illustration of something conceptualized but not completed, often a line drawing done with more precision than a sketch, intended to provide sufficient detail to allow the object to be fully realized. Executed as part of a design process, design drawing is distinct from art drawing and drafting.

designer binding
A bookbinding bearing decoration done by an artist skilled in graphic design, usually in a style contemporary with the period in which it was made. This type of binding began to appear in trade editions in the second half of the 19th century and remained popular into the early 20th century. Click here to see examples of 19th-century gold-stamped publisher's bindings done in designer-style (Rare Books and Manuscripts Library, Columbia University). For an example of 20th-century book design, see this binding by Paul Bonet (National Art Library, Victoria and Albert Museum). Click here and here to see other contemporary examples.

desk copy
A complimentary copy of a new book or recently revised edition provided without charge by the publisher as an instructor's copy when additional copies are ordered by a college or university bookstore for sale to students enrolled in a course of study. An examination copy may become a desk copy once an instructor decides to assign the work as required reading.

desk diary
A booklet containing blank pages organized by date and hour of the day, to be kept on a desk for recording appointments and other commitments.

desk dictionary
A single-volume dictionary of approximately 150,000 words intended for use by an individual sitting at a desk or in a workspace (example: Webster's New World Dictionary of the American Language). Entries usually indicate orthography, syllabication, pronunciation, etymology, and definition. Synonyms, antonyms, and brief biographical and gazetteer information are included in some editions. Synonymous with college dictionary. Click here to connect to the online version of Merriam-Webster's Collegiate Dictionary and Thesaurus. Compare with pocket dictionary and unabridged dictionary.

desk schedule
A list of the hours during which librarians and other public services staff are regularly assigned to assist users at the circulation desk, reference desk, information desk, or other public service point in a library, usually prepared by the staff member responsible for supervising operations performed at the location. See also: rotation.

desktop
The display on a computer screen at logon, usually consisting of clickable icons representing equipment, software, and data files, shown against a neutral background or decorative wallpaper.

desktop binding
Office technologies designed to allow the producer of a multipage document to securely fasten its leaves together, without sending it to a professional binder. An example is VeloBind, an electric punch and strip, hot-knife process often used to custom bind legal documents up to three inches (750 sheets) thick.

desktop publishing (DTP)
The use of microcomputer hardware and software for page layout, graphic design, and printing to produce professional-quality camera-ready copy for commercial printing at a fraction of the cost of using the services of a commercial publisher. Used extensively to produce in-house brochures, fliers, newsletters, posters, etc., DTP requires desktop publishing software and a high-speed PC equipped with a large monitor and high-resolution laser printer to produce text and graphics in WYSIWYG format. See also: self-publishing.

destruction
In archives, the process of obliterating records that are no longer of value but remain too sensitive to be simply discarded as trash. For paper records, the most common methods are shredding and pulping. Incineration is used for records in other physical formats. Electronic records may be rendered inaccessible by deletion, an operation that removes the pointer from an index without overwriting the data, but for more sensitive information in electronic format, the data must be overwritten several times or physically destroyed to render recovery impossible.

detached board
A condition in which the front or back board of a book has separated from the rest of the binding, usually along the joint (see this example). The remedy is rebinding. Compare with broken hinge.

detached pages
A condition in which one or more leaves of a bound publication have separated from the book block along the binding edge, a common problem in perfect bindings when the adhesive has dried and cracked (see these examples). A few loose pages can often be tipped in but when entire sections have detached, the remedy is rebinding.

detective fiction
A popular novel, short story, or drama in which the details of a crime (or suspected crime) are uncovered by an amateur or professional sleuth who searches for clues and interprets them, often using ingenious methods to solve the mystery of "Who done it?" The modern detective story began with Edgar Allan Poe's Murders in the Rue Morgue (1841) and is now a popular subgenre of crime fiction. Sherlock Holmes, the eccentric sleuth created by Sir Arthur Conan Doyle, has become a household word in many English-speaking countries. The hard-boiled detective, at home in the criminal underworld, first appeared in pulp magazines in the 1920s and was brought to life in such film noir classics as John Huston's The Maltese Falcon, based on the novel by Dashiell Hammett. Period detective novels may qualify as historical fiction (example: The Chronicles of Brother Cadfael by Ellis Peters). Detective fiction is reviewed in The Mystery Review and The Drood Review of Mystery. For more information, see Classic Crime Fiction. See also: suspense.

deterioration
Damage that occurs to an item by physical, chemical, or biological means after it has been produced, usually over a period of time. The category includes bindings weakened by adhesives that dry out and crack, printing papers embrittled by acid, paper documents discolored by the growth of mildew under damp conditions, and the chemical decay of nitrate and acetate film base. For examples, see the Book Damage Gallery, courtesy of the MIT Libraries. Data recorded on some digital storage media also deteriorates over time, a phenomenon known as "bit rot." See also: inherent vice and stabilization.

Deutscher Bibliogtheksverband e.V. (DBV)
Founded in 1949 with headquarters in Berlin, the DBV (German Library Association) promotes library services and professional librarianship in Germany and publishes the journal Bibliotheksdienst. Click here to connect to the DBV homepage.

device
An ornament or symbol used in printing, such as the north pointer used on maps to indicate compass orientation. Also refers to an insignia used as a publisher's identifying mark, for example, the small design of a house stamped on the spine and printed on the title page of books published by Random House. Click here to view the anchor-and-dolphin device of Aldine press in a 16th-century edition of Ovid's Metamorphoses (Edinburgh University Library, Dd.6.75). See also: colophon.

Also refers to any electronic or electromagnetic machine or hardware component. Computer peripherals (printer, scanner, disk drives, etc.) require a program routine called a device driver to connect to the operating system.

devotional image
A picture of a religious figure or group of figures, often idealized and isolated from narrative context, intended to aid prayer, worship, or spiritual contemplation (see this example). Examples include Byzantine icons, holy cards, and Sunday school cards, which may include a brief text. Portraits of actual human beings declared saints may become devotional images (example).

Dewey, Melvil (1851-1931)
One of the founders of the American Library Association, Melvil Dewey served as editor of Library Journal from 1876 to 1881, published the Dewey Decimal Classification system in 1876, and served as librarian at Columbia University from 1883 to 1888, where he founded the first professional library school in 1887. He became the director of the New York State Library in Albany in 1888, taking the library school with him. Dewey was also a spokesman for professionalism in librarianship, for library education, and for equality of opportunity for women in the profession. A dynamic man, he also advocated standardization of library education, methods, tools, equipment, and supplies and was an advocate of spelling reform. To learn more about his life, see Irrepressible Reformer: A Biography of Melvil Dewey by Wayne Wiegand (American Library Association, 1996) or Wikipedia.

Dewey Decimal Classification (DDC)
A hierarchical system for classifying books and other library materials by subject, first published in 1876 by the librarian and educator Melvil Dewey, who divided human knowledge into 10 main classes, each of which is divided into 10 divisions, and so on. In Dewey Decimal call numbers, arabic numerals and decimal fractions are used in the class notation (example: 996.9) and an alphanumeric book number is added to subarrange works of the same classification by author and by title and edition (996.9 B3262h). Click here to see a list of DDC summaries.

Developed and updated continuously for the past 125 years, most recently by a 10-member international Editorial Policy Committee (EPC), DDC is the most widely used classification system in the world. According to OCLC, it has been translated into 30 languages and is used by 200,000 libraries in 135 countries. The national bibliographies of 60 countries are organized according to DDC.

In the United States, public and school libraries use DDC, but most academic and research libraries use Library of Congress Classification (LCC) because it is more hospitable. The abridged edition (ADC), intended for general collections of 20,000 or fewer titles, is a logical truncation of the notational and structural hierarchy of the full edition. OCLC has also developed WebDewey for classifying Web pages and other electronic resources. Click here to connect to the DDC Web site maintained by OCLC and here to read OCLC's Introduction to Dewey Decimal Classification. See also: Universal Decimal Classification.

diacritical mark
A mark written or printed above or below an alphabetic character to indicate its semantic or phonetic value, for example, the cedilla used in French under the letter ç (as in français) to indicate that it is pronounced like s or ts, instead of k.

diagnostics
Software designed to automatically test hardware components (disks, keyboard, memory, etc.) whenever a computer session begins, to determine if they are functioning properly. If a component fails on startup, a warning message appears on the screen.

diagram
A figure, chart, or graphic design intended to illustrate or explain a principle, concept, or set of statistical data. Also, a drawing, sketch, or plan that shows the steps in a process or the relationship of the parts of an object or structure to the whole, usually simplified for the sake of clarity and utility. Click here to see examples in a 12th-century manuscript copy of Boethius' De Musica (National Library of Australia) and here to see a copy of one of the first books to contain printed diagrams (University of Sydney Library). A diagram is usually accompanied by a line or two of explanation or by explanatory text, and the various parts of the illustration may be keyed to the text or caption by means of numbers or letters, with or without lines or arrows pointing to the appropriate features, as in this diagram of the skeleton of a bird.

In cartography, the term is sometimes applied to a schematic map characterized by highly simplified representation (click here to see a diagram of the subway system in Lisbon, Portugal). See also: block diagram and fence diagram.

DIALOG
A vendor that provides per-search access to a wide selection of online databases via a proprietary interface. Established in 1972, DIALOG led the market for many years in online information retrieval and remains strong in business, science, and technology. Now owned by Thomson, the company also provides technical support for Internet users and e-commerce. In most libraries, DIALOG searches are mediated by a specially trained librarian to keep costs down. Click here to connect to the DIALOG homepage.

dialog box
A small square or rectangular area that opens in a graphical user interface in response to a selection made by the user, usually providing additional information or listing other options and/or settings available at that point in the program. A dialog box differs from a window in being neither movable nor resizable. Some applications are designed to open a dialog box automatically when certain operations are selected, but this feature can usually be set "off" when not desired. Also spelled dialogue box.

dialogue
Conversation, real or imagined, between two or more persons, especially the exchange of ideas and opinions between individuals who do not share the same point of view. Also refers to a written work in the form of a conversation between two or more people or to the portions of a work of fiction (novel, short story, play, etc.) consisting of words spoken by the characters, as opposed to passages of narrative or description. In the text of a narrative work, dialogue is set apart by the use of quotation marks. Compare with monologue.

dial-up access
Connection to a network, online service, or computer system from a terminal or workstation via a telephone line, usually in exchange for payment of a monthly fee to a service provider, as opposed to access via a dedicated line. Dial-up access requires a modem to convert the digital signals produced by a computer into the analog signals used in voice transmission, and vice versa.

diamond
In bookbinding, an ornament in the shape of a rhombus, usually built up of small massed tools done in blind, ink, or gold. A lozenge is a rhombus-shaped decorative design with one axis longer than the other. Click here to see an example on the cover of a late 19th-century morocco binding (Otto G. Richter Library, University of Miami, Florida). To see other examples, try a search on the keyword "diamond" or "lozenge" in the British Library's Database of Bookbindings.

Diamond Sutra
The earliest-dated printed book known to exist, the Diamond Sutra was discovered in 1907 by British archaeologist Sir Marc Aurel Stein in the walled city of Dunhuang, an important military base on the Silk Road. Printed on seven strips of paper joined to form a scroll approximately 16 feet long and about 10 1/2 inches wide, its extraordinary state of preservation is attributed to the dryness of the climate in northwest China and the fact that it remained sealed inside a cave with thousands of Buddhist manuscripts and silk paintings for approximately 900 years. Earlier examples of block printing survive, but this Chinese translation of a work originally written in Sanskrit is the first bearing a date. Decorated with an elaborate frontispiece, the scroll has a colophon at the inner end, establishing the date of its creation as A.D. May 11, 868. Click here to view an image of the Diamond Sutra, courtesy of the Silkroad Foundation. The scroll is in the collections of the British Library.

diapering
From the French diapré, meaning "variegated." In manuscript illumination, a repetitive geometric pattern used as background in a miniature, initial letter, or border or as a filler for empty spaces. Michelle Brown notes in Understanding Illuminated Manuscripts (Getty Museum/British Library, 1994) that this style of decoration, used as early as the 11th century, was especially popular in Gothic illumination. For examples, see the 14th-century Breviary of Chertsey Abbey (Bodleian Library, University of Oxford, MS Lat. liturg.d.42) and the 14th-century Bible Historiale by the Master of Jean de Mandeville (Getty Museum, MS 1). Diapering is also used in decorative bookbinding, as in these these bindings in calf and morocco (University of Miami Libraries).

diary
A private written record of day-to-day thoughts, feelings, and experiences kept by a person who does not expect them to be published. Also refers to the blankbook or notebook in which such experiences are recorded. Diaries are sometimes published posthumously, and some have become famous literary and historical works, for example, the Diary of Samuel Pepys and more recently that of Anne Frank. Click here to see a collection of 19th-century women's diaries, courtesy of the Archives of Ontario, and here to see a 17th-century example, courtesy of the Connecticut State Library. Compare with journal and memoirs.

Also refers to a small notebook in which the consecutive dates of the year are listed, with blank space for scheduling appointments, meetings, important deadlines, etc.

In film and video, a work consisting of footage taken of the filmmaker's daily life, including long unedited or edited-in-camera sections (example: Filmmaker: A Diary by George Lucas [1968]).

diazo print
A document reproduced by passing ultraviolet radiation through a translucent original, exposing a sheet underneath, coated with diazonium salts. The UV light is blocked by the dark lines of the original, leaving the coating beneath the lines unexposed. When the coated sheet is exposed to ammonia vapor, the lines appear in blue, black, or brown against a white or clear background (see this example). Compare with blueprint. Synonymous with blueline print, diazotype, and dyeline print.

diced
A leather bookbinding decorated in a crisscross pattern of parallel diagonal lines forming rows of small diamonds across the surface. To see examples, try a search on the keyword "diced" in the British Library's Database of Bookbindings.

Dickinson classification
A library classification scheme, developed by George Sherman Dickinson (1886-1964), used to catalog and classify printed music, in which compositions are arranged according to five main categories and then by medium, form, and composer.

dictabelt
An audiorecording medium developed by the Dictaphone Corporation, consisting of a plastic sleeve that fits around a platen with a needle assembly capable of recording sound from a telephone line or radio frequency by cutting a groove into the sleeve as the platen is rotated (see this example). A single dictabelt can hold recordings of several conversations. Sound quality was better than on belts made by IBM which used a magnetic coating instead of grooves. Edison produced a similar product, the Voicewriter, which cut grooves into a thin, flat disc. Because the format is obsolete, preservation requires duplication in another medium. The Miller Center of Public Affairs at the University of Virginia provides online access to the dictabelt recordings of President John F. Kennedy.

dictionary
A single-volume or multivolume reference work containing brief explanatory entries for terms and topics related to a specific subject or field of inquiry, usually arranged alphabetically (example: Dictionary of Neuropsychology). The entries in a dictionary are usually shorter than those contained in an encyclopedia on the same subject, but the word "dictionary" is often used in the titles of works that should more appropriately be called encyclopedias (example: Dictionary of the Middle Ages in 13 volumes). See also: biographical dictionary and reverse dictionary.

A language dictionary lists the words of a language in alphabetical order, giving orthography, syllabication, pronunciation, etymology, definition, and standard usage. Some dictionaries also include synonyms, antonyms, and brief biographical and gazetteer information. In an unabridged dictionary, an attempt is made to be comprehensive in the number of terms included (example: Webster's Third New International Dictionary). An abridged dictionary provides a more limited selection of words and usually less information in each entry (Webster's New College Dictionary). In a visual dictionary, each term is illustrated. See also: desk dictionary and pocket dictionary.

Dictionaries are known to have developed from Latin glossaries as early as the 13th century. Dictionaries of the English language, limited to difficult words, were first compiled in the 17th century. Samuel Johnson's A Dictionary of the English Language, published in 1755, was the first to match in scope those produced by the academies of Continental Europe. The most famous contemporary example is the Oxford English Dictionary (1989), conceived in Britain in 1857 by the Philological Society. Some English language dictionaries are limited to a specialized vocabulary (example: Dictionary of American Slang). In libraries, at least one large printed dictionary is usually displayed open on a dictionary stand. Smaller portable editions are shelved in the reference section. Abbreviated dict. Compare with concordance and thesaurus. See also: lexicography, polyglot dictionary, reverse dictionary, and rhyming dictionary.

This Web site is an example of an electronic dictionary. OneLook is a metadictionary that indexes English words and phrases in over 900 online dictionaries, including Merriam-Webster OnLine, with translation into other languages. Click here to connect to the Yahoo! list of online dictionaries.

dictionary catalog
A type of catalog, widely used in the United States before the conversion of the card catalog to machine-readable form, in which all the entries (main, added, subject) and cross-references are interfiled in a single alphabetic sequence, as opposed to a catalog divided into separate sections by type of entry (author, title, subject). Compare with classified catalog.

dictionary stand
A free-standing piece of display furniture usually made of wood, at least waist-high with a sloping top and a book stop, used in libraries to display an open dictionary or other large reference work. A dictionary stand is narrower than an atlas case and may contain shelves for storing other volumes. Small revolving table-top models are also available from library suppliers. To see examples of various models, try a keywords search on the term in Google Images.

didactic literature
Fiction and poetry intended primarily to teach the reader a lesson. The category includes cautionary tales and morality tales. See also: fable and parable.

differential pricing
The controversial practice of charging libraries a substantially higher price for periodical subscriptions than the amount an individual subscriber is required to pay, which some journal publishers claim is justified because a library subscription makes the publication available to more readers, a phenomenon known in the publishing trade as pass-along. Also refers to the practice in Europe of charging North American subscribers a rate substantially higher than normal, presumably because they can afford to pay more.

diffuse authorship
A work created by four or more persons or corporate bodies in which no single individual or body can be identified as the primary author. In libraries, such works are cataloged under the title, with an added entry for the first-named person or body. In AACR2, if three or fewer persons or bodies are primarily responsible for the work, main entry is under the heading for the first-named author, with added entries for the other principal authors. Compare with unknown authorship. See also: mixed responsibility and shared responsibility.

digest
An orderly, comprehensive abridgment or condensation of a written work (legal, scientific, historical, or literary), broader in scope than a synopsis, usually prepared by a person other than the author of the original. Headings and subheadings may be added to facilitate reference. In law, a summary of existing laws, reported cases, and court decisions arranged systematically for quick reference. The earliest digests, treatises on Roman law compiled by classical Roman jurists, were copied by medieval scribes in manuscript form, sometimes with glosses and illumination.

Also refers to a periodical or index containing excerpts or condensations of works from various sources, usually arranged in some kind of order (example: Book Review Digest). Some digests have been digitized (example: International Digest of Health Legislation published by the World Health Organization).

digital
Data recorded or transmitted as discrete, discontinuous voltage pulses represented by the binary digits 0 and 1, called bits. In digitized text, each alphanumeric character is represented by a specific 8-bit sequence called a byte. The computers used in libraries transmit data in digital format. Compare with analog. See also: born digital.

The term is also used in a general sense to refer to the wave of information technology generated by the invention of the microcomputer in the second half of the 20th century, as in the expressions "digital divide" and "digital library."

digital archaeology
The process of reclaiming digital information that has been damaged or become unusable due to technological obsolescence of formats and/or media. The most common causes of damage are storage under conditions of high temperature and/or relative humidity, contact with magnetic fields, natural disaster (i.e., lightning strikes), manufacturer's defects, and normal wear-and-tear. Reclamation techniques vary.

digital archive
A system designed for locating, storing, and providing access to digital materials over the long term. A digital archive may use a variety of preservation methods to ensure that materials remain usable as technology changes, including emulation and migration. The National Digital Information Infrastructure and Preservation Program (NDIIPP) led by the Library of Congress is an example of a program aimed at preserving digital content. Compare with digital archives. See also: digital repository

digital archives
Archival materials that have been converted to machine-readable format, usually for the sake of preservation or to make them more accessible to users. A prime example is American Memory, a project undertaken by the Library of Congress to make digital collections of primary sources on the history and culture of the United States available via the Internet. Also refers to information originally created in electronic format, preserved for its archival value (see digital archive).

digital asset management (DAM)
Systems designed to organize and display digital content produced in a variety of media types. The content is usually locally owned and controlled, rather than licensed from a third party. Most of the DAM systems offered by the leading library automation vendors use standards other than the MARC record, such as XML, the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH), Metadata Encoding and Transmission Standards (METS), and JPEG2000. The rapid pace of archival and special collections digitization projects has created the need for DAM systems. Synonymous with digital object management. Compare with electronic resources management.

Digital Audio Broadcasting (DAB)
Radio broadcasting technology, developed during the 1980s and launched by the BBC in 1995, in which analog audio is converted into digital signals for transmission on an assigned channel in the AM or FM frequency range. DAB provides higher quality sound than analog transmission and offers more radio programs over a given spectrum than FM radio, but is not as robust. For this reason, although DAB is used in several countries, particularly in Europe, it has not replaced FM transmission in popularity. Synonymous with digital radio and high-definition radio.

digital collection
A collection of library or archival materials converted to machine-readable format for preservation or to provide electronic access (example: The Papers of Thomas Jefferson: Digital Edition, a project of the University of Virginia Library. Also, library materials produced in electronic formats, including e-zines, e-journals, e-books, reference works published online and on CD-ROM, bibliographic databases, and other Web-based resources. In the United States, the Digital Library Federation is developing standards and best practices for digital collections and network access. In the meantime, the National Information Standards Organization (NISO) has published A Framework of Guidance for Building Good Digital Collections (2007).

Digital Compact Cassette (DCC)
A digital magnetic tape audiorecording medium introduced in 1992 by Philips and Matsushita as a successor to the standard analog audiocassette (see this example). In the same year, SONY introduced the digital MiniDisc (MD), but despite their technical superiority neither format seriously challenged the analog audiocassette, which was eventually superseded by the digital compact disc (CD).

digital curation
The active management, enhancement, and preservation of trustworthy digital research data for the duration of its lifecycle. Digital curation entails verification of the integrity of digital data, selection of authoritative digital data for its long-term value, creation of digital objects and associated metadata, transfer of digital objects to reliable digital repositories for secure storage, provision of access to designated users, and periodic re-evaluation of digital formats to avoid obsolescence. Click here to learn more about digital curation, courtesy of the Digital Curation Centre (DCC).

digital divide
A term coined by former Assistant Secretary of Commerce for Telecommunication and Communication Larry Irving, Jr., to focus public awareness on the gap in access to information resources and services between those with the means to purchase the computer hardware and software necessary to connect to the Internet and low-income families and communities that cannot afford network access. Public libraries are helping to bridge the gap between information "haves" and "have-nots" with the assistance of substantial grants from industry leaders such as Bill Gates of Microsoft. The E-rate established by the Telecommunications Act of 1996 (TCA) has helped schools, public libraries, and rural health care institutions bridge the gap. Digital Divide Network is a Web site devoted to the issue. Synonymous with information gap.

digital elevation model (DEM)
A digital representation of cartographic information in the form of a raster grid of regularly spaced elevation values for ground positions derived primarily from the conversion of contours on printed topographic map series and from photogrammetry (click here to see a DEM of Lake Tahoe). Resolution depends on the distance between adjacent grid points. The U.S. Geological Survey publishes 7.5-minute DEMs derived from its 1:24,000- and 1:25,000-scale topographic quadrangle maps; 30-minute DEMs corresponding to the east half or west half of its 30-minute by 60-minute topographic quadrangle maps; and 1-degree DEMs corresponding to the 3 arc-second (or 1:250,000-scale) topographic map series. DEMs can be combined with other digital data to provide additional visual detail (see this example of a digital orthophoto overlaid on a DEM). Click here to learn more about digital elevation models, courtesy of the USGS. Click here to see a practical application of digital elevation modeling in the conservation of the mountain gorilla. Synonymous with digital terrain model. See also: National Elevation Dataset.

digital image
An analog image that has been converted, usually by a scanner or digital camera, into a gridded array (matrix) of small discrete locations called picture elements ("pixels") that hold binary data quantifying the size in area of the location and the color and brightness (spectral intensity) of the image at the location. The data of which a digital image is comprised can be stored on a computer, manipulated, transmitted electronically, printed, reproduced on film, or displayed on a computer monitor or television screen. Digital imaging is a rapidly developing technology. Click here to see examples of digital images, courtesy of the Victoria & Albert Museum (London), or search the Prints & Photographs Online Catalog (PPOC) at the Library of Congress.

digital imaging
The field within computer science covering all aspects of the capture, storage, manipulation, transmission, and display of images in digital format, including digital photography, scanning, and bitmapped graphics. In libraries, images of text documents are created for electronic reserve collections and digital archives. They are also available in full-text bibliographic databases and reference resources. Click here to connect to the digital imaging program the Library of the University of Illinois, Urbana-Champaign. Resources for Digital Imaging are also listed on a Web page maintained by Conservation OnLine (CoOL).

Digital Libraries Initiative (DLI)
A multi-agency interdisciplinary research program of the National Science Foundation (NSF) that provides grants to facilitate the creation of large knowledge bases, develop the information technology to access them effectively, and improve their usability in a wide range of contexts. Click here to see a list of projects funded by DLI Phase 2.

digital library
A library in which a significant proportion of the resources are available in machine-readable format (as opposed to print or microform), accessible by means of computers. The digital content may be locally held or accessed remotely via computer networks. For a distributed example, see the Mountain West Digital Library established by the Utah Academic Library Consortium. In libraries, the process of digitization began with the catalog, moved to periodical indexes and abstracting services, then to periodicals and large reference works, and finally to book publishing. Abbreviated d-lib. Compare with virtual library. See also: Digital Library Federation, Digital Public Library of America, and National Science Digital Library.

Digital Library Federation (DLF)
A consortium of major libraries and library-related agencies dedicated to promoting the use of electronic technologies to extend collections and services, DLF is committed to identifying standards and best practices for digital collections and network access, coordinating research and development in the use of information technology by libraries, and assisting in the initiation of projects and services that individual libraries lack the means to develop on their own. Click here to connect to the homepage of the DLF.

digital line graph (DLG)
A file of digital vector representations of cartographic information, specifically planimetric and topographic map features (points, lines, and areas) derived from aerial photographs or from cartographic source materials using manual or automated digitizing methods (see this example). DLGs can be viewed without any background image or overlaid on orthophotographs and other images (click here to see a DLG of Lake Tahoe). They require much less file space than image data and can be resized without loss of clarity, in contrast to raster data, which becomes pixilated if enlarged too much. Large-scale (1:24,000 or 1:25,000), intermediate-scale (1:100,000), and small-scale (1:2,000,000) DLG data files are available from the U.S. Geological Survey for various categories of data (hydrography, hypsography, transportation, political boundaries, Public Land Survey System data, etc.). Click here to learn more about USGS DLGs. Compare with digital raster graphic.

digital media lab (DML)
A space in a library, designed to give patrons access to hardware and software needed to create digital media, including videorecordings, sound recordings, podcasts, ebooks, Web sites, digital images, and animation (see this example at the Skokie Public Library in Illinois). DMLs are often Mac-based. Staff training is required.

Digital Millennium Copyright Act (DMCA)
Legislation passed by Congress and signed into law in October 1998 to prepare the United States for the ratification of international treaties protecting copyrights to intellectual property in digital form, drafted in 1996 at a conference of the World Intellectual Property Organization (WIPO). The bill was supported by the software and entertainment industries and opposed by the library, research, and education communities. Click here to learn more about the DMCA, courtesy of the Electronic Frontier Foundation (EFF). A summary is available from the U.S. Copyright Office at www.copyright.gov/legislation/dmca.pdf. See also: Technology, Education and Copyright Harmonization Act.

digital object
In the technical sense, a type of data structure consisting of digital content, a unique identifier for the content (called a "handle"), and other data about the content, for example, rights metadata. See also: digital asset management and Digital Object Identifier.

Digital Object Identifier (DOI)
A unique code preferred by publishers in the identification and exchange of the content of a digital object, such as a journal article, Web document, or other item of intellectual property. The DOI consists of two parts: a prefix assigned to each publisher by the administrative DOI agency and a suffix assigned by the publisher that may be any code the publisher chooses. DOIs and their corresponding URLs are registered in a central DOI directory that functions as a routing system.

The DOI is persistent, meaning that the identification of a digital object does not change even if ownership of or rights in the entity are transferred. It is also actionable, meaning that clicking on it in a Web browser display will redirect the user to the content. The DOI is also interoperable, designed to function in past, present, and future digital technologies. The registration and resolver system for the DOI is run by the International DOI Foundation (IDF). CrossRef is a collaborative citation linking service that uses the DOI. Click here to learn more about the DOI.

digital orthophotograph (DOP)
A black and white or infrared aerial photograph taken with digital equipment, instead of a conventional film camera, then rectified to eliminate displacement and other image distortions to conform to measurements taken on the ground (this example). A DOP has uniform scale and can be used like a map. DOPs can also be combined in a photomosaic to create a single image of a larger area, or with other digital products such as digital elevation models (DEMs) to provide additional detail. Click here to see digital orthophotographs used in a study of the Waller Creek floodplain in Texas. Click here to learn more about orthoimagery, courtesy of the U.S. Geological Survey. Abbreviated digital orthophoto. See also: digital orthophoto quadrangle.

digital orthophoto quadrangle (DOQ)
The standard product for the initial national orthoimagery coverage of the United States, the DOQ is a digital orthophotograph at a scale of 1:12,000 centered on a quarter-quadrangle at 1-meter pixel resolution (click here to see a DOQ of Lake Tahoe). DOQs are cast on the Universal Transverse Mercator (UTM) projection from black and white or color infrared digital aerial photographs. Each DOQ includes an ASCII keyword header containing descriptive information about the image data, including photographic source type, date taken, software systems used in creating it, and production date of the digital elevation model (DEM) metadata used in the orthophoto rectification process. 3.75-minute DOQs are available from the U.S. Geological Survey. Click here to learn more about USGS DOQs. Synonymous with digital orthographic quadrangle and digital orthophoto quarter-quadrangle (DOQQ).

Digital Performance Right in Sound Recordings Act of 1995 (DPRA)
Legislation amending U.S. copyright law to extend the scope of copyright protection afforded sound recordings by giving copyright holders the exclusive right to perform copyrighted works publicly by means of digital audio transmission, for example, via digital audio cable services, satellite music services, and other digital subscription services. Broadcasting is specifically exempted from the DPRA. Click here to read the text of the DPRA.

digital preservation
The process of maintaining, in a condition suitable for use, materials produced in digital formats, including preservation of the bit stream and the continued ability to render or display the content represented by the bit stream. The task is compounded by the fact that some digital storage media deteriorate quickly ("bit rot"), and the digital object is inextricably entwined with its access environment (software and hardware), which is evolving in a continuous cycle of innovation and obsolescence. Also refers to the practice of digitizing materials originally produced in nondigital formats (print, film, etc.) to prevent permanent loss due to deterioration of the physical medium. Click here to learn about the National Digital Information Infrastructure and Preservation Program, a collaborative initiative of the Library of Congress. The Digital Preservation Coalition (DPC) was established in 2001 to address the challenges of preserving digital resources in the UK. Synonymous with e-preservation and electronic preservation. See also: digital archive, LOCKSS, National Digital Information Infrastructure and Preservation Program, and preservation metadata.

Digital Public Library of America
A proposed national digital library for the United States. Currently in planning, DPLA received initial funding from the Alfred P. Sloan Foundation in 2010, and an additional $5 million in grants in 2011, including $2.5 million from the Arcadia Fund based in London. Robert Darnton, historian and university librarian at Harvard University, has been one of the strongest public voices in support of the concept. Harvard's Berkman Center for Internet and Society took the planning initiative, setting up a wiki and a LISTSERV and organizing working groups, each responsible for a different "workstream" (governance, content and scope, audience and participation, financial/business models, legal/copyright issues, and technical aspects). John Palfrey, professor of law at Harvard and faculty co-director of the Berkman Center, chairs the DPLA steering committee. At a plenary meeting in October 2011 at the National Archives in Washington, D.C., the digital library project Europeana agreed to work with DPLA to promote interoperability. The target date for DPLA to go "live" is April 2013. Click here to learn more about DPLA.

digital publishing
The activities involved in the business of preparing, processing, producing, protecting, and preserving information content in digital form, whether the result is delivered in print or electronic format (e-journal, e-book, Web document, etc.). In 2005, the Pennsylvania State University Libraries formed a partnership with Penn State Press to create an Office of Digital Scholarly Publishing which will use new media technology to advance scholarly communication at Penn State and within the wider academic community. One goal of the new Office will be to make research publications available online by moving existing print journals and monographs to a digital environment. The role of libraries in digital publishing is discussed by Kate Wittenberg in the article Librarians as Publishers: A New Role in Scholarly Communication in the November/December 2004 issue of Searcher. For a full treatment of the topic, see The Columbia Guide to Digital Publishing edited by William Kasdorf (Columbia University Press: 2003).

digital raster graphic (DRG)
A digital image of a standard-scale topographic quadrangle originally published on paper by the U.S. Geological Survey, including all marginal data, optically scanned at high resolution (250 or more dots per inch). The image inside the neat line is georeferenced to the surface of the earth, with horizontal positional accuracy and datum matching that of the source map (click here to see a DRG of Lake Tahoe). DRGs can be used as background images on which other digital data is overlaid and as base maps in any GIS, GPS, or graphics software system capable of displaying GeoTIFF images. DRGs can also be combined with other digital products, such as digital elevation models (DEMs) and digital orthophoto quadrangles (DOQs) to provide additional visual detail. Click here to learn more about USGS DRGs. Compare with digital line graph. See also: raster data.

digital reference
Reference services requested and provided over the Internet, usually via e-mail, instant messaging ("chat"), or Web-based submission forms, usually answered by librarians in the reference department of a library, sometimes by the participants in a collaborative reference system serving more than one institution. For an example, see Ask a librarian... from the Library of Congress. Synonymous with chat reference, e-reference, online reference, real-time reference, and virtual reference. See also: MARS: Emerging Technologies in Reference Section.

digital repository
Many academic and research libraries are actively engaged in building digital collections of books, papers, theses, media, and other works of interest to the institution served, as a means of preserving and disseminating scholarly information. Usually locally authored or produced, content can be either born digital or reformatted. Access is generally unrestricted, in compliance with the Open Archives Initiative (OAI) protocol for metadata harvesting, which makes such archives interoperable and cross-searchable (see this example maintained by the University of Texas Libraries). Click here to learn more about the role of digital repositories in scholarly communication, courtesy of the Association of Research Libraries (ARL).

digital rights
Ownership of information content published and distributed in electronic format, protected in the United States by copyright law. Digital rights management (DRM) uses technologies specifically designed to identify, secure, manage, track, and audit digital content, ideally in ways that ensure public access, preserve fair use and right of first sale, and protect information producers from uncompensated downloading (copyright piracy).

The Copyright Clearance Center (CCC) provided one of the earliest solutions used by libraries to obtain permissions. Since the late 1990s, a variety of models have emerged to facilitate the complex relationships and transactions among rights, works, and the parties that produce and use information, including encryption schemes and plug-ins. ContentGuard has based its software approach on XrML (eXtensible rights Markup Language), originally developed at Xerox PARC, which the company hopes will become the open standard for interoperability, giving customers a common platform for receiving content under conditions that protect copyright.

digital rights management (DRM)
A system of hardware and software components and services, designed to distribute and control the rights to intellectual property created or reproduced in digital form for distribution online or via other digital media, in conjunction with corresponding law, policy, and business models. DRM systems typically use data encryption, digital watermarks, user plug-ins, and other methods to prevent content from being distributed in violation of copyright.

Unfortunately for consumers and libraries, "quick fix" DRM solutions often fail to distinguish between copyright piracy and fair use, may undermine the first sale provision of U.S. copyright law, and can be draconian. For example, many e-book editions completely forbid copying, even for works in the public domain. Carrie Russell, copyright specialist for the American Library Association (ALA), also contends that some DRM solutions threaten "to reduce the functionality of consumer and library electronic equipment, including desktop computers" (Library Journal, August 2003). Click here to learn more about DRM, courtesy of Wikipedia. The Electronic Privacy Information Center (EPIC) provides a Web page on Digital Rights Management and Privacy. See also: DRM-free.

digital talking book (DTB)
Unlike the traditional audiobook, which is an analog representation of a print publication, the digital talking book is a collection of electronic files arranged as a multimedia representation of information traditionally imparted in print. Special playback equipment is required. DTBs enable the target population to receive information as human or synthetic speech, refreshable Braille, or alternative visual display (e.g., large print). When created and assembled in accordance with the ANSI/NISO Z39.86 Specifications for the Digital Talking Book (2005), the files make possible such features as rapid, flexible navigation; bookmarking and highlighting; keyword(s) searching; spelling of words on demand; and user control over the presentation of footnotes, page numbers, etc., enabling readers with physical and visual disabilities to access information flexibly and efficiently, and sighted users with learning or reading disabilities to receive information through multiple senses.

digital thesis
A master's thesis or Ph.D. dissertation created in electronic form ("born digital"). Most universities require a paper or microform copy for archival purposes, but for some hypermedia theses, a print version may not be an accurate representation of the original (or even possible). Preservation dilemmas posed by the rapid obsolescence of digital equipment and formats underscore the need for standards. See the Networked Digital Library of Theses and Dissertations (NDLTD) and the Australasian Digital Theses Program (ADT).

digitization
The process of converting data to digital format for processing by a computer. In information systems, digitization usually refers to the conversion of printed text or images (photographs, illustrations, maps, etc.) into binary signals using some kind of scanning device that enables the result to be displayed on a computer screen. In telecommunication, digitization refers to the conversion of continuous analog signals into pulsating digital signals. The Association of Research Libraries (ARL) has endorsed digitization as an accepted preservation reformatting option for a range of materials.

Mass digitization is the conversion of texts or images to digital format on a very large scale using robotic equipment capable of scanning hundreds of pages per hour (see this example). After raising billions of dollars in an initial public stock offering, Google and five major research libraries (the University of Michigan, Harvard University, Stanford University, Oxford University, and the New York Public Library) announced in December 2004 plans to digitally scan over 10 million unique books over the next decade and make them searchable online, the largest digitization project ever attempted. Since the announcement, publishers and other stakeholders have expressed concerns and raised issues about the legal, social, economic, and other impacts of the project and similar initiatives that will inevitably follow. British spelling is digitisation. See also: book digitizer.

dime novel
A melodramatic fictional narrative of adventure, romance, and action published in inexpensive paperback edition in the United States during the second half of the 19th century, sold mainly at newsstands for 10 to 25 cents a copy. The term originated with the Dime Novel Library introduced in 1860 by Beadle and Adams of New York. Hundreds of thousands of titles, written according to formula, were issued before this pulp fiction genre waned in the early 20th century. Among of the most popular was Buffalo Bill, King of the Border Men (1869) by E.Z.C. Judson, writing under the pseudonym Ned Buntline. His other works included Bigfoot Wallace, the Giant Hero of the Border (1891) and The Red Warrior, or, Stella DeLorme's Comanche Lover: A Romance of Savage Chivalry (1869). The influence of the dime novel on popular culture is studied by literary historians. For online exhibitions, try Dime Novels and Penny Dreadfuls (Stanford University Libraires), the Dime Novel Cover Art Gallery (Syracuse University Library), and Dime Novels at the Library of Congress. Compare with penny dreadful and yellowback.

dimensions
The actual physical size of a bibliographic item, given in centimeters in the physical description area of the bibliographic description unless some other unit of measurement is more appropriate (millimeters for film reels, inches for sound discs, etc.). See also: height and width.

diminuendo
The practice of gradually reducing the height of the letters following a large initial letter in a medieval manuscript or early printed book until they are the same size as the script or type used for the text. Michelle Brown notes in Understanding Illuminated Manuscripts (Getty Museum/British Library, 1994) that this practice was particularly popular among the scribes of Ireland and Britain from about A.D. 550 to 900. Prime examples are the incipit pages in the Lindisfarne Gospels, an illuminated masterpiece produced in Northumbria at the end of the 7th century, currently in the custody of the British Library.

dimpled
The condition of a book which has, on its covers or pages, one or more a small indentations, similar to those on a golf ball.

ding
A nick or dent that has left a visible impression on the covers or dust jacket of a book, sometimes the result of careless handling or storage.

dingbat
Synonymous, in the United States, with printer's flower.

diorama
A three-dimensional museum exhibit or display on any scale in which inanimate objects and lifelike figures are carefully arranged in front of a two-dimensional background scene drawn or painted in perspective on a flat or curved surface to create the illusion of greater depth of field than actually exists. Special lighting and recorded sound effects are often added to make the impression more realistic. Small portable examples are made for traveling exhibits. To see examples, try a keyword search on the term in Google Images.

diploma
A document written or printed on paper of fine quality (often resembling parchment), certifying that an academic degree was conferred on the student or honoree whose name appears on the document, by the educational institution in whose name the degree is granted, on a specific date, also indicated. Diplomas are normally awarded at an annual graduation ceremony and may be acquired by libraries as part of the personal papers of the recipient of the degree. To see examples, try a keyword search on the term in Google Images.

diplomatics
The branch of paleography devoted to the study of the creation, form, and transmission of archival records, especially handwritten documents, and their relationship to the facts contained in them and to their creator(s), as a means of validating or disconfirming provenance and authenticity. Diplomatics requires detailed examination of the internal and external characteristics of documents, such as the materials on which they are written, the script or hand used by the writer, and the language in which they are written (vocabulary, usage, literary style, etc.). The first major work on diplomatics was the six-volume De Re Diplomatica or "The Study of Documents" (1681; supplement, 1704) by the Benedictine monk Jean Mabillon.

diptych
A portable tablet consisting of two shallow hinged boxes made of wood, ivory, or metal filled with a layer of beeswax on the inside, on which the ancient Greeks and Romans wrote with a stylus. When warm, the wax surface could be easily erased by rubbing, then written over.

Also refers to pictures or designs painted or carved on the inside surfaces of two tablets hinged or mounted to form a single work, often devotional images used as altarpieces (see this 13th-century example in ivory and this 14th-century example in silver gilt, courtesy of the Metropolitan Museum of Art). In medieval Europe, triptychs were sometimes used for the same purpose--images on three tablets hinged so that the outer tablets folded over the center panel (see the Stavelot Triptych, courtesy of the Morgan Library). Compare with pugillaria. See also: polyptych.

direct access
The use of an electronic resource by means of a physical carrier (disk, cassette, cartridge, etc.) designed to be inserted into a computer or its auxiliary equipment, as opposed to accessing the resource remotely via a network (AACR2). Although disks and CD-ROMs are still used for some applications, most libraries in the United States have shifted to networked digital resources available from vendors on subscription. Compare with remote access.

Also refers to the ability to use information without need of an intermediary.

direct connection
A permanent leased line linking a computer or computer system to a network such as the Internet. Faster than a dial-up connection, a direct connection can also be used at any time of day.

direct delivery
Putting library materials directly into the hands of the patron who requests them, without requiring a trip to the library to pick them up, for example, through a books-by-mail service. Direct delivery is practical for special libraries located on the premises of the host organization. It is also used by public libraries on a limited scale to serve homebound users.

direct edition
An edition of a work for which the author provides the publisher with camera-ready copy produced on a computer with the aid of word processing software. Used mainly for works that cannot be produced economically from type.

direct entry
The principle in indexing that a concept describing the content of a bibliographic item should be entered under the subject heading or descriptor that names it, rather than as a subdivision of a broader term; thus a book about "academic libraries" would be assigned the heading Academic libraries, not Libraries--Academic.

directional
Said of a question that can be answered at the information desk or reference desk by sending the patron to the location of specific resources, services, or facilities within the library, as opposed to a question requiring substantive information, instruction in the use of library resources, or referral to an outside agency or authority. See also: signage.

directive
An order, regulation, bulletin, or similar communication of instructions issued in writing, usually by a central office, military command, or other authority, with the expectation of compliance (see this historic example, courtesy of the Truman Presidential Museum & Library). Military directives may be classified at time of issuance.

direct mail item
A government document sent directly to a depository library in the Federal Depository Library Program (FDLP) from the GPO printing plant or the contractor via first or second class mail, rather than with a regular shipment of materials, and not included on a shipping list. Direct mail items are typically publications that must arrive as quickly as possible. As more federal documents have become available electronically on the date of issuance via FDsys, the number of direct mail titles has been reduced by including them in regular shipments to save postage costs. Click here to learn more.

director
The person who has overall responsibility for controlling and supervising the performance of a work written for stage or screen, whose name appears in the credits at the beginning or end of a motion picture, videorecording, or television program and is indicated in the note area of the bibliographic record representing the work in the library catalog. Compare with producer, and screenwriter. See also: library director.

direct order
An order for materials placed by an acquisitions librarian directly with the publisher, rather than through a jobber or subscription agent. The percentage of orders placed in this manner has declined as wholesalers and subscription services have positioned themselves to offer economies of scale to their customers and services that add value. Some publishers no longer accept direct orders and sell only to wholesalers (example: Random House).

director's cut
After initial shooting is completed, the film director refines the editor's cut to make the film an expression of his or her artistic vision. Under rules established by the Directors Guild of America (DGA), directors have at least ten weeks after completion of primary shooting to prepare their first cut. If additional shooting is required, the editing process may take longer. See also: final cut.

directory
A list of people, companies, institutions, organizations, etc., in alphabetical or classified order, providing contact information (names, addresses, phone/fax numbers, etc.) and other pertinent details (affiliations, conferences, publications, membership, etc.) in brief format, often published serially (example: American Library Directory). In most libraries, current directories are shelved in ready reference or in the reference stacks. See also: city directory, telephone directory, and trade directory.

An Internet directory is an online service that indexes publicly accessible Web sites and other Internet resources, usually by subject according to a hierarchical classification system (example: Yahoo! Directory). INFOMINE is a searchable directory that indexes only scholarly Internet resource collections. The WWW Virtual Library is an example of a metadirectory (directory of directories).

In data storage and retrieval, a catalog of the files stored on the hard disk of a computer, or on some other storage medium, usually organized for ease of access in a hierarchical tree of subdirectories. The topmost directory is called the root directory. See also: FTP.

In library cataloging, the portion of the MARC record following the leader, which serves as an index to the tags included in the record, normally hidden from view of both cataloger and catalog user. Constructed by the cataloging software from the bibliographic record at the time the record is created, the directory indicates the tag, length, and starting location of each variable field. Whenever a change is made in the record, the directory is automatically reconstructed.

Directory of Open Access Journals (DOAJ)
Launched in May 2003 from Lund University in Sweden, DOAJ lists over 1,000 fully peer-reviewed open access journals reporting original research in the sciences, social sciences, and humanities in all languages, with records that can be easily downloaded by librarians and entered in an online catalog. Approximately 25 percent of the journals are searchable at the article level. Click here to connect to the DOAJ homepage.

dirty copy
In publishing, a manuscript or typescript containing so many corrections and/or additions that it is difficult to read. The opposite of clean copy.

dirty proof
In printing, a proof of typeset copy containing many errors or one returned to the printer heavily corrected. A clean proof contains no errors or corrections.

disaster
An unexpected event that puts library or archival collections at risk of serious damage or destruction, the most catastrophic being fire, flood, and earthquake. Well-prepared libraries have a disaster plan in place for handling various kinds of emergencies. Click here to see the damage to the Hamilton Library caused by the 2004 flood at the University of Hawaii, Manoa. See also: disaster preparedness.

disaster plan
A set of written procedures prepared in advance by the staff of a library to deal with an unexpected occurrence that has the potential to cause injury to personnel or damage to equipment, collections, and/or facilities sufficient to warrant temporary suspension of services (flood, fire, earthquake, etc.). In archival records management, securing vital records in the event of disaster is one of the highest priorities. An effective disaster plan begins with a thorough risk assessment to identify the areas most vulnerable to various kinds of damage and to evaluate measures that can be taken in advance to ensure preparedness. Both an initial action plan and a recovery plan should be included. The California Preservation Program provides this Library Disaster Plan Template. Compare with contingency plan and emergency plan.

disaster preparedness
Steps taken by a library or archives to prepare for serious damage to facilities, collections, and/or personnel in the event of a major occurrence such as a fire, flood, or earthquake, including preventive measures, formulation of an effective disaster plan, maintenance of adequate insurance, etc. Click here to connect to the disaster preparedness section of Conservation OnLine (CoOL).

disbound
A book or other printed publication from which a previous binding has been removed, usually in preparation for rebinding, part of the process called pulling. Click here to see the steps in the process, courtesy of the Bancroft Library, UC Berkeley. Compare with unbound.

disc
A generic term used in computing to distinguish read-only digital storage media (audio compact discs, CD-ROMs, videodiscs, etc.) from those that are rewritable. Also, an alternate spelling of disk ("optical disc" or "optical disk").

discard
To officially withdraw an item from a library collection for disposal, a process that includes removing from the catalog all references to it. Also refers to any item withdrawn for disposal, usually stamped "discard" to avoid confusion. Materials are usually withdrawn when they become outdated, cease to circulate, wear out, or are damaged beyond repair. When shelf space is limited, duplicates may be discarded to make room for new acquisitions. Withdrawn items may be exchanged or given as gifts to other libraries, but the most common method of disposal is in a book sale. Unsold items may be given to a thrift store or thrown away as trash, depending on the policy of the library. See also: weeding.

Depository libraries receiving materials through the Federal Depository Library Program (FDLP) are legally required to retain a federal document for a minimum of 5 years, unless it is a duplicate copy or has been superseded by a more recent edition. Publications withdrawn after the 5-year retention period are offered to other depository libraries (see needs and offers). Under Title 44 U.S.C, documents that have been offered but not requested by another depository may then be discarded. See also: superseded list.

discharge
In circulation, to cancel the record of a loan upon return of the borrowed item and payment of any overdue fine. Compare with charge. See also: patron record.

discipline
An organized branch of human knowledge, developed through study and research or creative endeavor, constituting a division of the curriculum at institutions of higher learning. A discipline may be divided into subdisciplines, for example, biology and zoology within the biological sciences. In Western scholarship, the disciplines are traditionally organized as follows:

Arts and humanities: archaeology, classical studies, communication, folklore, history, language and literature, performing arts (dance, film, music, theater), philosophy, religion and theology, visual arts
Social sciences: anthropology, criminology and criminal justice, economics, international relations, law, political science, psychiatry, psychology, public administration, social work, sociology, urban studies, women's studies
Sciences: astronomy, biology, chemistry, computer science, earth sciences, mathematics, medicine and health, physics

In Dewey Decimal Classification (DDC), the classes representing subjects are arranged according to discipline (example: 150 for Psychology).

disclaimer
A legal notice posted on a Web page, appended to an e-mail message, given on a product, or provided with a service informing the reader or consumer that the host or producer does not guarantee and cannot be held responsible for all aspects of content or performance.

disclosure
The act of making something known by revealing it to public scrutiny. In the information sector, disclosure is usually made by the provider in a voluntary statement informing the user of any financial or personal interest in the content provided or in its provision, for example, payment made by the owners of a Web site to a Web search engine to get the site listed or payment received by the owners of a Web site from the manufacturer or distributor of a product or service recommended by the site. Lack of disclosure, a common problem on the Internet, may affect the credibility of information available online.

disclosure-free extract
A copy of a record made available for public use from which information has been selectively removed in compliance with provisions of open records or privacy laws. In the United States, this means the exclusion of all information exempted under the Freedom of Information Act (FOIA) and the Privacy Act of 1974. Synonymous with public use file.

discography
A list or catalog of audiorecordings, usually of works by a specific composer or performer, in a certain style or genre, or of a specific time period. Each entry in a discography provides some or all of the following descriptive elements: title of work, name of composer and performer(s), date of recording, name of manufacturer, manufacturer's catalog number, and release date (see this online example). Also refers to the systematic cataloging of audiorecordings and to the study of sound recording as a medium of expression. The person who compiles such a catalog is a discographer. Compare with filmography.

discontinuation
In Dewey Decimal Classification (DDC), the shifting of a topic or the entire contents of a class number to a more general number in the same hierarchy, or the complete removal of the topic or number from the schedule, usually because the current literature on the topic or concept has dwindled significantly or because the distinction represented by the number is no longer valid or recognized in the field. A note is added to explain the shift or removal, and the discontinued number is enclosed in square brackets. See also: relocation and schedule reduction.

discontinued
A serial publication for which a library subscription or continuation order has ended. In the catalog record for the title, the library's holdings are indicated in a closed entry. See also: canceled and ceased publication.

discontinued number
In Dewey Decimal Classification (DDC), a class number from an earlier edition no longer used, indicated at the appropriate location in the schedules by a note to "class in" a more general number. A discontinued number is enclosed in square brackets. See also: schedule reduction.

discount
A percentage deducted from the price of any product or service, for example, the reduction in the rate paid for telecommunication services by schools and public libraries under the federal E-rate program. In publishing, a percentage deducted from the publisher's list price for an item as an inducement to purchase. In book sales, the discount system includes:

Cash discount - usually 1-2 percent, offered by publishers to booksellers in exchange for payment within 30 days or less
Continuation order discount - for automatic shipment of works published as serials (usually 5 percent)
Convention discount - on orders placed at a publisher's exhibit during a conference or convention (usually 15 percent)
Library discount - on purchases by libraries and related institutions (usually 5-10 percent)
Prepayment discount - for payment with the order (usually 5 percent or free shipping)
Prepublication discount - on orders placed prior to the publication date to encourage advance sales
Professional or courtesy discount - offered to individuals at publisher's discretion
Quantity discount - on purchases of a required number of copies or titles
Short discount - on professional books and textbooks sold directly to individuals and sometimes on special orders (less than trade discount)
Trade discount or long discount - to jobbers and retail outlets, usually 30-45 percent or better, depending on publisher and quantities ordered

See also: consortial discount.

discourse analysis
Linguistic analysis of segments of spoken or written language that are longer than one sentence and form a unit having recognizable structure for the purpose of identifying regularities in the occurrence of phonological, grammatical, and semantic elements. In computer science, the results of discourse analysis have been applied to the study of human/computer interaction, for example, in the development of voice recognition systems.

discovery service
A single interface, providing integrated access to the multiple information resources (catalogs, publishers' e-book and e-journal collections, subscription databases, archival collections) to which a library has rights. Discovery systems use consolidated subject indexing and metadata. Search results are generally deduped and relevance ranked (example: EBSCO Discovery Service). For an in-depth discussion of discovery services see the article by William Miller in the March 2012 issue of Library Issues.

disinformation
The deliberate, often covert, dissemination of erroneous information, usually with the intention of influencing by deception the actions or opinions of another, a technique used in foreign relations and armed conflict to mislead an adversary. Compare with misinformation. See also: propaganda. The Center for Media and Democracy (CMD) maintains the online resource SourceWatch to monitor disinformation in the public sector.

disintermediation
Elimination of the mediator or "middleman." In the delivery of information services, the need for professional assistance is minimized in user-friendly systems designed to facilitate end-user searching. See also: mediated search.

disk
A generic term used in computing for a digital storage medium that is rewritable, as opposed to read-only. Compare with disc. See also: magnetic disk and optical disk.

disk drive
In computing, a generic term for the hardware component that physically manipulates a specific type of magnetic disk (hard, floppy, WORM, Zip), allowing the user to read data from and write data to it. Disk drives can be internal or external. Also spelled disc drive.

dismissal
Termination of employment at the instigation of the employer, usually for cause (incompetence, malfeasance, physical or mental incapacity, genuine financial exigency, etc.). An employment contract may specify the conditions under which dismissal is warranted and require the employer to give the terminated employee severance pay or a minimum period of notice in which to find other employment. Compare with resignation.

dispersal
In records management, a method of ensuring the survival of records by maintaining duplicate copies in different physical locations, usually reserved for essential records because of the additional expense. Duplicates may be created on paper, microfilm, magnetic tape, or other permanent medium, as part of regular operating procedure. If the records are electronic, the necessary hardware and software must be maintained to access them when needed. Vital records are often protected in this way because they provide direct evidence of legal status, ownership, obligations incurred, etc., making them irreplaceable in the event of disaster.

displacement
In the projection of sound motion picture film, the sound elements are read inside the projector after the film passes the lens through which the image is projected. To synchronize sound and picture, the sound tracks are not recorded alongside the corresponding images, but instead precede them by a fixed number of frames that varies with film gauge and type of sound track, for example, for 16mm film the displacement is 28 frames for magnetic track and 26 frames for optical track.

display
For purposes of copyright (17 USC 101), to show a work or copy of a work, either directly or by means of film, slide, television image, or any other device or process or, in the case of a motion picture or other audiovisual work, to show individual images nonsequentially. A work is publicly displayed when shown directly at a place open to the public or where a substantial number of persons outside the normal circle of a family and its social acquaintances is gathered; or by transmission to members of the public in the same place or in separate places and at the same time or at different times.

display case
A box or set of shelves enclosed in glass or plexiglass to allow books and other items to remain protected while on exhibit. A display case can be free-standing, wall-mounted, or built-in. Modern designs are usually lockable. Cases used for perishable museum specimens may be climate-controlled to prevent deterioration. Click here and here to see examples. Synonymous with exhibit case. Compare with display rack.

display constant
A term, phrase, and/or spacing or punctuation convention that may be system-generated to render the visual presentation of data in a bibliographic record more meaningful to the user. The display text is not carried in the record but an indication for it (based on tags, indicators, subfield codes, or coded values) is. In MARC 21, suggested display constants and examples are provided in the separate formats for authority data, bibliographic data, classification data, community information, and holdings data. Use and display of the constants is determined by the individual organization or system.

display copy
A copy of a new book or other publication put on view, usually in a bookstore or as part of publisher's exhibit at a conference or convention. At the end of the event, display copies are sometimes sold to conference participants at a discount, especially if their dust jackets are no longer in new condition.

display matter
Any printed matter that is not part of the text of a work, including illustrations, headings, captions, printer's ornaments, etc. To distinguish it from body matter, textual display matter is set in type of a different size and/or font.

display panel
In medieval manuscripts, a decorative section of a page, usually rectangular in shape, containing display script, often following an ornamented initial letter. Click here to see an example in a 13th-century manuscript, courtesy of the Library of Congress and Bibliothèque Nationale de France.

display rack
A library furnishing in metal, wood, or plastic designed to display printed material, such as brochures, announcements, instructional handouts, reading lists, etc., face-forward to encourage users to browse and select what they need. Sold by library suppliers, display racks are available in wall-mounted and free-standing designs, from small countertop models to large floor units. Compare with display case.

display script
A decorative calligraphic script in which the letterforms are more elaborate and generally larger than the script used for the text. In medieval manuscripts, display script was often used following a large initial letter to emphasize a major division of the work. In some cases, each letter was written in ink of a different color, and the script might be enclosed in a decorative display panel. The corresponding term in printing is display type. Click here to view display script used in an early illuminated volume of medical writings (Special Collections, Glasgow University Library, MS Hunter 96 T.4.13) and here to see an example in a 12th-century Gospel book (Koninklijke Bibliotheek).

display type
Type sizes larger than 14-point, used mainly for headings, titles, banners, and other display purposes, in contrast to the smaller text type used to print the body of the text and even smaller extract type used for quotations, notes, etc. The corresponding term in calligraphy is display script. See also: fancy type.

disposal
In U.S. government archives, the destruction of noncurrent records that are no longer needed. Also used synonymously with disposition.

disposition
The manner in which the noncurrent records of an agency or individual are handled once their utility has been appraised, whether stored (temporarily or permanently) in a repository in their original format, reproduced and stored on microform, sold, donated, or destroyed. Compare with disposal. See also: disposition schedule.

disposition schedule
A systematic list of documents used by an archivist to determine: (1) which of the recurring records of an agency or individual will be retained, (2) the period of time for which they will be held, (3) where they will be housed during the retention period (archives or intermediate storage), and (4) any other decisions concerning their disposition, based on their utility and value to the organization (see this example). Synonymous with records schedule and retention schedule. See also: sentencing.

dissertation
A lengthy, formal written treatise or thesis, especially an account of scholarly investigation or original research on a specialized topic, submitted to a university in partial fulfillment of the requirements for a Ph.D. degree. Dissertations submitted at universities in the United States, Canada, Great Britain, and other European countries are indexed and abstracted in Dissertation Abstracts International (DAI), available in print, on CD-ROM, and online from ProQuest. In most academic libraries, copies of dissertations may be requested on interlibrary loan or ordered via document delivery service. Abbreviated diss. Compare with thesis.

Dissertation Abstracts International (DAI)
A service that provides indexing and abstracting of Ph.D. dissertations and master's theses in all academic disciplines submitted at universities in the United States, Canada, Great Britain, and European countries since 1861. Dissertations have been abstracted since 1980 and theses since 1988. DAI is available from ProQuest in print, on CD-ROM, or as an online bibliographic database, or via OCLC FirstSearch (updated monthly). Paper copies of dissertations can be ordered from Dissertation Express on a fee-per-item basis.

distance learning
A method of instruction and learning designed to overcome barriers of time and space by allowing students to study in their own homes or at local facilities, often at their own convenience, using materials available electronically or by mail. Communication with the instructor is normally by telephone or e-mail. Telecommunication networks and teleconferencing have facilitated distance learning. Libraries are working to support distance learning by providing online catalogs and databases, electronic reserves, electronic reference service, online tutorials, and electronic document delivery service. The Association of College and Research Libraries has published Standards for Distance Learning Library Services (2008). See also: continuing education and Distance Learning Section.

Distance Learning Section (DLS)
The section of the Association of College and Research Libraries (ACRL) within the American Library Association (ALA) that provides leadership, support, and new ideas for librarians involved in all aspects of distance learning. Click here to connect to the DLS homepage.

distinctive title
A title that is unique to a specific work. Distinctiveness of title is important in registering copyright and makes the entry for a document easier to retrieve from a library catalog or other finding tool in a search by title.

distortion
In electronic transmission, alteration in a signal waveform as it passes from input to output of a system or device, sometimes used intentionally for special effect, for example, in rock music. In audio systems, the result of unwanted distortion is poor fidelity in the reception or reproduction of transmitted or recorded sound. Subjectively, some forms of distortion are more objectionable than others. Also used synonymously in bookbinding with warping.

distribution
The sale, lease, loan, syndication, and rental of moving image works or recordings for any purpose, including exhibition. Also, the sale of a new book or edition by a publisher other than the company that issued the title, for example, by a publisher in another country.

distribution copy
In reprography, a microform copy from which additional copies of equal legibility can be reproduced.

distribution imprint
The statement printed on the verso of the title page of a book giving the official name(s) of the distributor(s) from which copies can be obtained, as distinct from the imprint of the publisher that issued the edition or the printer responsible for printing the edition.

distribution list
In e-mail software, a feature that allows the user to establish a list of e-mail addresses under a common name, enabling messages to be sent simultaneously to everyone on the list when addressed to the list name. Although the term is sometimes used synonymously with mailing list, the latter generally supports a much larger group, requiring special software for automatic maintenance.

distribution rights
Legal arrangements made by a publisher to transfer to another company or person the exclusive right to market a publication, usually within a designated geographic area. In books, distribution rights are usually indicated in the distribution imprint on the verso of the title page.

distributor
An agent or agency that owns the exclusive or shared rights to market a publication or other item, usually within a designated geographic area. In domestic publishing, the distributor is usually but not always the publisher. Foreign publications are often distributed by a domestic publishing company under an agreement with the original publisher. Abbreviated distr. See also: distribution imprint.

dit
In old French literature, a short poem or story in verse, often treating a homely subject in a didactic or satirical manner. In medieval manuscripts, collections of dits are sometimes interspersed with lyric and musical pieces, as in this example by the 14th-century poet and composer Guillaume de Machaut (Library of Congress/Bibliothèque Nationale de France).

diversity
Inclusiveness with regard to differences in age, gender, sexual orientation, religious belief, and ethnic, racial, or cultural background within a given population. In the United States, libraries strive to achieve diversity in library school admissions, hiring, collection development, services, and programs. See also: affirmative action and Office for Diversity.

divided catalog
In the 1930s, when it became apparent that dictionary catalogs were becoming cumbersome, large libraries in the United States began dividing their catalogs into two sections, one for subject entries and the other for main and added entries other than subject (authors, titles, series, etc.). Eventually, some libraries divided their catalogs into three sections (author, title, and subject). Divided catalogs have the disadvantage of requiring the user to know in advance which type of entry is needed (entries for works written by a specific author are filed separately from works written about the same person), but once the initial determination is made, the user is spared the time and effort of looking through entries that are not of the type desired. Synonymous with split catalog. See also: classified catalog.

divide-like note
A note added to a heading in a classification schedule to inform the cataloger that the heading is subdivided in the same way as another heading in the same schedule. See also: pattern heading.

Divine Office
Literally, a duty performed for God. Prayers performed daily at certain hours of the day and night by priests, clerics, and members of monastic orders. The Divine Office and the Mass form the basis of Roman Catholic liturgy. The practice originated in services performed in the Jewish synagogue and the Apostolic Church, each office consisting of a recitation of Psalms and lessons read from Scripture. Over the centuries, hymns, antiphons, canticles, and other elaborations were added. By the close of the 6th century, the eight canonical hours were fixed at: matins (2:30 a.m.), lauds (5:00 a.m.), prime (6:00 a.m.), terce (9:00 a.m.), sext (12:00 noon), none (3:00 p.m.), vespers (4:30 p.m.), and complin (6:00 p.m.). The prayers of the Divine office are contained in the breviary. Its lay counterpart is the Book of Hours. Click here to learn more about the Divine Office as it relates to medieval manuscripts.

divinity calf
A style of binding used in the mid-19th century for theological and devotional works, characterized by plain covers in smooth khaki or dark brown calfskin, usually with beveled boards and blind-tooled single-line borders ending in Oxford corners, with the edges of the sections often stained red.

division
In Dewey Decimal Classification, the first level of subdivision of the 10 main classes, usually representing a discipline or subdiscipline, indicated by the first two digits in the notation (example: 94 in 940 European history). There are 100 divisions in DDC (10 x 10). The next level of subdivision, indicated by a third digit other than zero, is called a section (944 for works on the history of France). Click here to download DDC summaries in PDF format, courtesy of OCLC.

Also, a separate major unit or department within a larger organization, for example, the Reference and User Services Association (RUSA) of the American Library Association (ALA) or the Canadian Association of Public Libraries (CAPL) within the Canadian Library Association (CLA). The divisions of the ALA and CLA have their own by-laws, officers, publications, etc., but some administrative functions, such as membership, Web site design and maintenance, etc., may be handled by the parent organization. A division may sponsor its own conference, as with of the Association of College and Research Libraries (ACRL) of the ALA, or hold its annual meeting in conjunction with that of the parent organization. Click here for a comprehensive list of the divisions within the ALA.

divisional title
The title printed on the recto of the leaf preceding the first page of the text of a major division of a book, sometimes with the number of the division, if numbered. The verso is normally left blank. Synonymous with part title and section title.

dLIST
Established in 2002, dLIST Digital Library of Information Science and Technology is a cross-institutional, subject-based, open access digital archive for the information sciences, currently hosted by the School of Information Resources and the Library Science and Learning Technologies Center at the University of Arizona. dLIST also offers copyright research and deposit service to participants. At present, dLIST is entirely grant-supported. Click here to connect to the dLIST homepage.

docket
An identifying statement concerning a letter or other document, attached to its outer surface or cover. Also, a brief written summary of the contents of a document (synonymous in this sense with abstract).

Also refers to a calendar of pending legal cases (trial docket) or of business matters to be transacted (agenda). Also, an official memorandum of the proceedings in a legal action (see this example).

docking station
A piece of computer hardware that enables a laptop to function as a desktop computer by providing a single large plug and socket that duplicates the individual cable connections to monitor, keyboard, mouse, and printer. Some docking stations include built-in peripherals such as audio speakers and CD-ROM drive and a network interface card to allow the user to connect to a local area network. Because no standard exists for docking stations, compatibility with the specific type of laptop is an important consideration in the decision to purchase. To see examples, try a keywords search on the term in Google Images.

doctored
A book that has been altered from its original condition, usually as a consequence of mending, repairs, restoration, or the addition or removal of parts. Compare with as issued. See also: made-up copy.

docudrama
A shortened form of the term documentary drama, a dramatization of events that actually happened, usually produced for film or television. Although some elements may be fictionalized, a serious attempt is made to be historically accurate (example: Edward Hopper, the Silent Witness, a film by Wolfgang Hastert). Compare with documentary and feature film.

document
A generic term for a physical entity consisting of any substance on which is recorded all or a portion of one or more works for the purpose of conveying or preserving knowledge. In the words of the communication theorist Marshall McLuhan, a document is the "medium" in which a "message" (information) is communicated. Document formats include manuscripts, print publications (books, pamphlets, periodicals, reports, maps, prints, etc.), microforms, nonprint media, electronic resources, etc. Abbreviated doc. See also: core document, documentary editing, document delivery service, false document, government documents, and internal document.

Also, any form printed on paper, once it has been filled in, especially one that has legal significance or is supplied by a government agency, for example, an application for copyright protection.

Also refers to a word processing text file (file type .doc) or any file created on a Macintosh computer.

documentarian
A person who makes one or more documentary motion pictures. Notable examples include Robert Flaherty (Louisiana Story and Nanook of the North), Ken Burns (Baseball and Jazz), and Michael Moore (Bowling for Columbine and Fahrenheit 9/11). Academy Awards are given annually for the best documentary feature and short subject. Also, a photographer who specializes in a form of photojournalism devoted to producing objective, usually candid photographs of a particular subject (often a person) for publication or exhibition.

documentary
A motion picture that records actual events or depicts social conditions creatively but without fictionalization, often through the use of historical footage and still photographs, usually accompanied by a narration dramatically structured to highlight important individuals who participated in the action. The term was coined by the Scottish filmmaker John Grierson in the late 1920s to describe the cinematic works of Robert Flaherty, the first person to produce films of social commentary depicting actual people in real-life situations (examples: Louisiana Story and Nanook of the North). When actuality is dramatized for emotional impact, the result is historical fiction or propaganda. Documentaries may include re-enactments, but the category does not include films that use realistic techniques to tell a fictional story. Documentary television series include American Experience, FRONTLINE, NATURE, NOVA, etc. Compare with docudrama and feature film. See also: actuality, cinema verité, documentarian, and mockumentary.

documentary editing
The scholarly selection, description, and critical annotation of original documents and historical and literary texts (letters, speeches, etc.) for publication, a process that contextualizes such works by presenting them in the company of related documents. According to Richard Pearce-Moses in A Glossary of Archival and Records Terminology, the early publication of historical documents was motivated, in part, by the wish to ensure their preservation through the distribution of many copies, and to make the works of historic persons more accessible, in keeping with the 19th-century romantic belief in the inspirational nature of historic texts. Click here to read a brief history of documentary editing, courtesy of the Association for Documentary Editing (ADE), the professional organization of documentary editors in the United States. Click here to learn about a documentary editing project underway at the University of Glasgow.

documentation
The process of systematically collecting, organizing, storing, retrieving, and disseminating specialized documents, especially of a scientific, technical, or legal nature, usually to facilitate research or preserve institutional memory. Also refers to a collection of documents pertaining to a specific subject, especially when used to substantiate a point of fact. See also: documentation center.

In scholarly publication, the practice of citing the source of a direct quotation or excerpt, an idea that is not original, or factual information, to support a thesis or argument and/or avoid plagiarism or infringement of copyright, particularly important in the writing of history and biography. See Research and Documentation Online, a Web site maintained by Diana Hacker, author of The Bedford Handbook.

In archives, the process of writing and organizing descriptions of records for reference purposes and to facilitate the development of finding aids for users.

In data processing, detailed descriptive information required to develop, operate, and maintain machine-readable data files and systems. In a more general sense, a systematic written description of any procedure (or set of procedures and/or policies), including the history of its application within a specific context.

In France, the term is used in nearly the same sense as information science.

documentation center
An organization or agency that specializes in receiving, processing, preserving, abstracting, and indexing publications, usually within a scholarly discipline or field of research and study (example: ERIC). Documentation centers also issue bulletins on the progress of such work for distribution to interested parties and may also prepare bibliographies on special topics, make copies or translations, and engage in bibliographic research.

document camera
A tabletop device used in bibliographic instruction and other visual presentations to project text and/or images from an opaque surface or transparency onto a large screen using an LCD projector. Document cameras have superseded overhead projectors in well-equipped libraries. To see examples, try a keywords search on the term in Google Images.

document delivery service (DDS)
The provision of published or unpublished documents in hard copy, microform, or digital format, usually for a fixed fee upon request. In most libraries, document delivery service is provided by the interlibrary loan office on a cost-recovery basis. The patron is usually required to pick up printed material at the library, but electronic full-text may be forwarded via e-mail. Also refers to the physical or electronic delivery of documents from a library collection to the residence or place of business of a library user, upon request. Click here to connect to DocDel.net, a directory of document suppliers provided by Instant Information Systems. See also: Ariel and electronic document delivery.

document supplier
A commercial company, agency, or library that provides copies of documents on request, usually for a fixed fee. Jean Shipman of Virginia Commonwealth University maintains an online list of Document Delivery Suppliers or try the DocDel.net directory. A printed list of document suppliers is provided in the front matter of the reference serial Magazines for Libraries.

document trail
All the authenticated sources of information about a topic, recorded in any medium, traced backward in time to determine conclusively the origins of an existing state of affairs, a technique used in archives to establish provenance and in news reporting to uncover the details of a story.

Document Type Definition (DTD)
A formal description of a particular type of document content, for example, a metadata record in SGML or XML declaration syntax, giving the names of data elements and rules for their use (where they may occur, whether they may repeat, etc.). DTDs are expected to be replaced by a new standard called XML Schema, a superset of DTD.

dog-eared
The condition of a book that shows definite signs of wear on the corners, especially pages that have been folded down at a corner to mark the reader's place (see this example).

doggerel
Versification that is loose, irregular, crude, and/or superficial due to the writer's ineptitude or by intention, usually for comic effect, as in John Skelton's Colin Clout:

For though my rhyme be ragged,
Tattered and jagged,
Rudely rain-beaten,
Rusty and moth-eaten,
If ye take well therewith,
It hath in it some pith.

To learn more about doggerel, see Wikipedia. Also spelled doggrel.

Dolby
A series of noise reduction systems developed by Dolby Laboratories for use in analog magnetic tape recording, designed to enhance signal-to-noise ratio by employing dynamic pre-emphasis during recording and dynamic de-emphasis during playback. Dolby A was introduced in 1966 for use in professional recording studios; Dolby B, a simpler but less effective system, was developed in 1968 for the consumer market and by the mid-1970s had become standard on commercially prerecorded music audiocassettes. Widespread adoption of digital audio has rendered Dolby analog noise reduction systems obsolete.

DOM
An abbreviation of digital object management. See: digital asset management.

domain
All the hardware and software resources controlled by a single computer system. In a local area network (LAN), all the clients, servers, and devices under the control of a single security database, administered under a common set of rules and procedures. On the Internet, all the clients, servers, and devices sharing a common portion of the IP address, the highest level domain being the type of entity serving as network host, indicated by the top level domain code at the end of the domain name. In database management, all the possible values of the data contained in a specific field present in every record in a file.

In indexing, the range or extent within which documents or items are selected for inclusion in a bibliography, index, or catalog. When the domain is one or more tangible collections, the result is a catalog. In an abstracting and indexing service, the domain is usually the published literature of an academic discipline (example: Sociological Abstracts) or group of related disciplines (Child Development Abstracts and Bibliography). In a national bibliography, the domain is the published output of an entire country. See also: scope.

In cartography, a set of possible values for an attribute, for example, the values "multilane highway," "two-way highway," "paved road," and "unpaved road" for the attribute "road type" as indicated on a road map. In an enumerated domain, the values are listed, as in the preceding example. In a range domain, the values (usually numeric) form a series, sequence, or scale measured in units within limits (minimum and maximum), as in the case of average annual precipitation. In a codeset domain, the values are determined by a set of codes, for example, the zip codes used by the U.S. Postal Service. Metadata standards for geographic information systems (GIS) require type of domain to be stated for each attribute (see this example).

domain name
The address identifying a specific site on the Internet. In the United States, domain names usually consist of three parts separated by the period (full stop). In the address www.thisuniversity.edu, the first part (www) indicates the protocol or language used in accessing the address, the second part (.thisuniversity) represents the name of the institution or organization hosting the site, and the last part (.edu) is a top level domain code indicating type of entity serving as network host. For the United States, the six basic top level domain codes are:

.com - commercial enterprise
.edu - educational institution
.gov - government agency
.mil - military installation
.net - network
.org - nonprofit organization

The top level domain for a country other than the United States is represented by a two-character alphabetic country code. For example, in the URL www.bbc.co.uk, the code .uk indicates that the commercial Web site is hosted in the United Kingdom. Other top level domain codes have been approved by ICANN, the technical body authorized to assign globally unique Internet identifiers, but the new codes are not widely used. For more information on the assignment of domain names, see ICANN Watch.

Domain Name System (DNS)
A distributed Internet directory service used primarily to translate numerical IP addresses (example: 123.456.78.9) into the alphanumeric domain name addresses (www.thisuniversity.edu) familiar to Internet users, and vice versa. The DNS is administered by the Internet Corporation for Assigned Names and Numbers (ICANN).

Domesday Book
The earliest surviving public record in England, the Domesday Book gives the results of a comprehensive survey of land-holding and duties to give tax and military service taken in England at the order of William the Conqueror in 1085. Written on parchment, the manuscript fills 913 pages and covers over 13,000 places in England and parts of Wales. Unprecedented in Europe at the time, the scale of the survey was not matched in Britain until the 19th-century census. Click here to learn more about the Domesday Book, courtesy of the National Archives of the UK.

domestic comedy
A form of situation comedy in which a continuing cast of characters, usually members of a middle-class suburban family, find humor in the resolution of everyday domestic problems and conflicts, in ways that strengthen and promote traditional family values (examples: the Life of Riley and The Brady Bunch).

donation
In archives, a voluntary deposit of records by a person or organization in which both legal title and physical custody are formally transferred by the donor to the institution maintaining the archives. In libraries, the term is used synonymously with gift. See also: donor file.

donor agreement
A formal written agreement between the person or organization donating archival materials to a library, archives, or other institution and the recipient, which (1) describes the materials, (2) specifies the nature of the transaction (gift, deposit, loan, purchase, or a combination of these), (3) states the responsibilities of the depository for the physical maintenance and accessibility of the materials, and (4) clarifies any rights in and restrictions on use of the materials by the depository, its patrons, or the donor, including copyright. A copy of the donor agreement is retained by the recipient in the donor file for purposes of documentation and reference. Synonymous with deposit agreement.

donor base
In fund-raising, the range of individuals and groups that can be relied on to support the institution through donations, based on characteristics such as age, gender, ethnicity, income, etc. As a general rule, the broader the base, the more successful will be the fund-raising campaign. To broaden their donor base, library fund-raisers seek to develop strategies that appeal to diverse elements within the population served.

donor file
A systematic record of the names of persons and/or organizations that have donated materials to a library or archives. A well-maintained donor file should document any restrictions on the preservation, use, or disposition of donated items (or files) and provide current contact information. In a weeding project, it is wise to check discards against such a file to ascertain if a prior agreement was made with the donor concerning final disposition. See also: donor agreement.

donor recognition
The use of ceremony and/or visual markers to identify by name a person (or persons) contributing to the acquisition of a library resource or facility or to the provision of a new service. Memorial bookplates are often used to indicate the donor of a specific item or collection (see this example), or the person in whose name materials are purchased with donated funds. Memorial nameplates and plaques may be attached to furnishings and equipment purchased in this manner (see this example). When a very large gift is received, a room or entire library may be named after the donor, who is normally honored in the formal opening ceremony.

doodle
An abstract or representational drawing or scribble, done aimlessly or absent-mindedly, often while preoccupied or waiting. The word was originally used in England during the 17th century, in reference to a fool or simpleton ("Yankee Doodle"). To see examples, try a keywords search on the term in Google Images.

door stop
Library slang for a piece of equipment so obsolete that it cannot be given away. Such items are usually consigned to a storage room in the basement until renovation or a move into a new facility makes disposal unavoidable.

DOQQ
An abbreviation of digital orthophoto quarter-quadrangle. See: digital orthophoto quadrangle.

DOS
An acronym for Disk Operating System (pronounced "dahss"), the first operating system for IBM-compatible personal computers, developed for IBM in a version called PC-DOS by Bill Gates' fledgling company Microsoft. Gates subsequently marketed the Microsoft version (MS-DOS) that became the underlying control program for early versions of Windows. Windows NT and later versions of Windows are not dependent on DOS, although they are capable of supporting DOS applications. Because it is nongraphical, line-oriented, and command-driven, the DOS interface is not as user-friendly as Windows.

dos-à-dos
A type of novelty binding in which two books are bound back-to-back, sharing the back cover, with the fore-edges of one aligned with the spine of the other, so that they open in opposite directions. Popular during the 17th century, this style was used to bind in a single volume the New Testament with the Prayer Book and Psalms (see this example). To see other examples, try a keywords search on the term "dos-a-dos" in the British Library's Database of Bookbindings. Compare with tête-bêche.

dossier
A French loanword for a number of documents purposefully collected from a variety of sources to supply information about a topic, especially a person, group of people, or specific matter of concern to the compiler (click here to see an online example, courtesy of the BBC). Because of its use in intelligence and espionage, the word has acquired a slightly sinister connotation. A dossier may be housed in one or more file folders or boxes or in some other container, depending on the amount of assembled material. According to Richard Pearce-Moses (A Glossary of Archival and Records Terminology), the term is also used interchangeably with "file" in the sense of a case file.

dot
A full stop used to divide the elements of an Internet address.

dot.com
A commercial enterprise that does all or a substantial portion of its business over the Internet, offering products and services for sale by credit card. One of the earliest and most successful examples is Amazon.com, which began by selling books online.

dot map
A thematic map on which small dots of uniform size and color are used to show the geographic and statistical distribution of a feature or phenomenon, each representing a certain number of the quantity being mapped, with widely spaced dots indicating sparse distribution and closely spaced dots, heavy distribution. Dots of different color can be used on the same map to show the distribution of more than one variable, or different aspects of the same variable. Click here to see a dot map showing the location of the nonmetro poor (U.S. Census Bureau) and here to see color-coded symbols indicating bird sightings as a function of time. Synonymous with dot density map. See also: graduated circle.

dots per inch (dpi)
In computing, a measure of image quality (resolution) in display and printing. On a typical computer screen, 72 dpi is acceptable, with 96 dpi the norm. In flat panels displays, 110 to 200 dpi is common. By comparison, 300 to 600 dpi is standard in printing.

double column
A book or other publication in which the text is set to half the width of a page, usually with a blank space or rule dividing the two columns, a format commonly used in bibles, dictionaries, encyclopedias, and other large-format reference works. Click here to see double column format used in the Gutenberg Bible (Ransom Center, University of Texas at Austin). Medieval manuscripts were often copied in double column format, and sometimes in triple column (see this 14th-century example, courtesy of the Koninklijke Bibliotheek).

double dagger (‡)
In printing, a character in the shape of a vertical stroke crossed twice, above and below the midpoint, used as the third-order reference mark, following the use of the asterisk (*) and the dagger (†). The double dagger is also known as a double obelisk or diesis.

double-fan adhesive binding
A type of adhesive binding in which the binding edge of the sections is milled and splayed, first in one direction while a slow-drying adhesive is applied, and then in the opposite direction as a second application is made, allowing the adhesive to penetrate no more than one thirty-second of an inch between the leaves, so that each leaf is tipped to the next. The method is not practical for books with a text block more than two inches thick. The strength of fan adhesive binding can be enhanced by notching the binding edge, but this technique has the disadvantage of restricting openability. Compare with perfect binding.

double hemisphere map
A map representing the entire surface of the earth or another celestial body, divided into two hemispheres, usually displaying the eastern hemisphere on the right and the western hemisphere on the left, sometimes connected down the center (click here to see a 17th-century decorated example, courtesy of the Library of Congress). To see other examples, try a keywords search on the phrase "double hemisphere and map" in Google Images. Compare with planisphere.

double image
In printing, two overlapping images, instead of one, formed when multiple plates are out of register (see this example). The same effect can occur in television reception when the signal, travelling over two paths of unequal length, arrives at slightly different times.

double leaf
A leaf twice the page size in a book, folded in half at the fore-edge or top edge, with the fold uncut and no printing inside the fold. When such a leaf is unnumbered, it is counted as two pages. In the bibliographic description of the item, the total number of pages is recorded as in the following example: [32] pp. (on double leaves). Synonymous with double fold. See also: Chinese style.

double numeration
A system of enumeration, used mainly in textbooks, law books, and technical publications, in which two numbers are assigned, usually separated by a period, hyphen, or other symbol, the first being the number of the chapter or other major division of the work, and the second indicating a section of the text or one of several illustrations, maps, graphs, charts, etc., numbered in the sequence in which they appear within the division, for example, Fig. 12.10 to indicate the tenth figure in chapter 12.

double plate
A single illustration that extends across facing pages in an open book or other publication, usually printed on a double-size leaf folded down the center and bound at the fold (see this example). A caption may be printed on the preceding or following page. Compare with double spread and face up. See also: plate.

double shelving
Storing books two rows to a shelf, one behind the other, a shelving method used in libraries only when space is severely limited. Shelves must be at least 10 inches deep for this alternative to work. The method can potentially double shelf capacity, but it reduces browsability and makes materials more difficult to locate and reshelve. These drawbacks can be minimized by installing graphic signage or limiting its use to series, such as legal case law, or to the back files of bound periodicals and reports. See also: flat shelving, fore-edge shelving, and shelving by size.

double slipcase
A slipcase constructed in two parts, one of which fits snugly inside the other, providing complete protection for the enclosed book. Also, a slipcase divided down the center to accommodate two volumes without contact between their covers (see this example).

double spread
Text and/or illustration printed across facing pages in a book or other publication, as if on a single page, usually for visual effect. Click here to see a map printed across facing pages in a 16th-century travel book, courtesy of the Royal Library of Denmark. Compare with double plate.

doublure
From the French doubler, meaning "to line." An ornamental panel of watered silk, satin, vellum, leather, decorated paper, or some other material of fine quality, used in place of the paste-down endleaf to line the inside of the boards in deluxe bindings. Morocco doublures were introduced in Europe during the late 15th century by Moorish binders working in Spain. Jane Greenfield notes in ABC of Bookbinding (Oak Knoll/Lyons Press, 1998) that doublures were popular from 1750 on, particularly in France, and that the turn-ins surrounding them were often gold-tooled. Click here to see doublures in tooled leather (Princeton University Library) and here to see a 19th-century example in beautifully decorated paper (University of North Texas Libraries). Synonymous with ornamental endpaper. See also: marbling.

doubtful authorship
A work for which authorship has not been conclusively established, which is ascribed to one or more persons on the basis of incomplete or unconvincing evidence. Some scholars believe the works of William Shakespeare to have been written by another author, but the evidence in support of this contention is inconclusive.

downgrade
The process of reducing the level of restrictions on access to classified materials to a lower security classification, often a step in the direction of declassification, the removal of all restrictions.

download
To transfer one or more files from a mainframe computer to a terminal, from a network server to a client computer, or from the hard disk of any computer to another storage medium. In libraries, downloading bibliographic data to floppy disk is a low-cost alternative to printing the results of an online search, and users are generally encouraged to do so. The opposite of upload.

down time
Any period during which a computer or system is out of operation, usually due to hardware or software failure or regular maintenance. In libraries, the amount of time a public access workstation or system is "down" is a measure of its reliability and can directly affect quality of service, particularly during periods of peak use. Also spelled downtime.

draft
A version of a document, in handwritten, typed, printed, or digital form, not intended to be final but instead subject to future modification (correction, revision, etc.), sometimes by a person or persons other than the original author. Click here to see the original proposal draft of the Bill of Rights of the United States of America submitted by Virginia, courtesy of the Karpeles Manuscript Library Museums. A rough draft usually provides only a preliminary or sketchy version of the work or plan. The last version of a work that has seen multiple revisions is the final draft. To avoid misunderstanding, a document not yet completed should be clearly marked "Draft." See also: bill.

drag
Pulling that occurs on the first and last sections or leaves of a bound volume as the covers are opened, caused by attachment of the endpapers directly to the sections (or leaves), as opposed to sewing them to the tapes or to a guard attached to the sections or leaves. When the endpapers are thin, drag may eventually result in a broken hinge. (Adapted from Bookbinding and the Conservation of Books: A Dictionary of Descriptive Terminology by Matt T. Roberts and Don Etherington).

drama
See: play.

dramatic musical work
A dramatic work that includes music as an integral part of the production. The category includes operas and operettas, musical plays and shows, and revues.

Dramatists Guild of America (DG)
Established in 1921, the Dramatists Guild is a professional association representing the interests of playwrights, composers, lyricists, and librettists writing for the living stage in the United States. In addition to providing contract services, the Guild assists dramatists in developing their artistic and business skills through its publications and educational programs. Click here to connect to the Guild homepage.

dramatization
An adaptation of a nondramatic work of fiction or nonfiction for performance on stage or screen, usually by a person other than the original author. In library cataloging, a dramatization is entered under the name of the playwright or screen writer, with added entries under the author and title of the work on which it is based. See also: novelization.

drawing
An abstract design or representational image made by inscribing lines on a surface using pen and ink, pencil (graphite), metalpoint, charcoal, chalk, pastel, crayon, etc. Unlike a print that can be produced in multiple copies, a drawing is unique. Also refers to the act of making such a work, as distinct from painting, normally done with one or more brushes dipped in ink or pigment. Click here to learn more about drawings, courtesy of the Getty Museum in Los Angeles. See also: architectural drawing, design drawing, figure drawing, line drawing, marginal drawing, mechanical drawing, outline drawing, sketch, technical drawing, tinted drawing, and underdrawing.

dress code
A set of written standards governing the proper attire and personal grooming of library employees when on duty, usually established by the library board and enforced by the library administration, to help maintain professionalism. Most codes require employees to be neat and clean and wear clothing in good condition and appropriate to their duties. Some codes also address recent fads such as body piercing and tattooing. Not all libraries have such a code.

drill
A strong, durable, coarse cotton fabric with a strong diagonal weave, sometimes used in bookbinding. Baseball caps and khaki uniforms are often made of drill.

driver
A program routine specifically designed to link a peripheral device to the operating system of a computer, allowing it to perform the functions requested by application software. Some drivers, such as the keyboard driver, are included in the operating system, but when a new piece of hardware is added to a computer (printer, scanner, disk drive, etc.), the appropriate driver must usually be installed on the CPU so that the operating system can call upon it to run the device. Also called a device driver.

DRM-free
Computer files without digital rights management (DRM) or restrictions on simultaneous use, printing, or downloading of content after it is sold. Music advertised as DRM-free is generally less expensive, but may also be of lower quality.

drollery
A small comic figure (or part of a figure) drawn or painted in the margin of an illuminated manuscript or hidden in a border or in the decoration of an initial letter. Christopher de Hamel suggests that drolleries and grotesques may have served as mnemonic devices, since medieval manuscripts were neither foliated nor paginated (The British Library Guide to Manuscript Illumination, University of Toronto, 2001). Click here to view an example drawn in ink in a 15th-century English missal (Bodleian Library, MS Don.b.6) and here to see examples in a 13th-century Spanish manuscript (Getty Museum, MS Ludwig XIV 6).

Drood Review of Mystery, The
Published since 1982, the bimonthly Drood Review of Mystery provides reviews of new mystery, suspense, and detective fiction, as well as author interviews, commentary on the genre, and guides to new titles for use in collection development, readers' advisory, and book discussions. ISSN: 0893-0252. Click here to connect to the Drood Review homepage. See also: Mystery Review, The.

drop
A telecommunication outlet in a library or other facility usually consisting of a voice jack and at least one data jack to allow users to physically connect to a computer network. See also: wireless.

drop-down title
The shortened version of the title of a book, printed on the first page of the text, usually the same as the running title. Compare with caption title.

drop initial
A large decorated or undecorated initial letter in a manuscript or printed work aligned horizontally with the tops of succeeding letters in the same line but extending below the line into a space left by indenting the next line (or lines). Drop initials are used mainly at the beginning of a chapter or other major division of a work. Click here to see an illuminated example in a 15th-century manuscript, here to see a decorated example in a 16th-century printed book, and here to see a 20th-century rubricated example (Cary Collection, Rochester Institute). Synonymous with drop cap. Compare with raised capital.

dropped heads
Chapter headings that start several lines down the printed page, uniformly throughout the book (see this example).

drop shipment
Publications ordered from a jobber by the acquisitions department of a library, sent by the publisher directly to the library at the request of the jobber, usually to reduce shipping costs when the jobber does not have the items in stock. Compare with reshipment.

drop side box
A book box, used mainly in preservation, with at least one side hinged to fall outward when opened, allowing the enclosed volume to be removed easily without damage. Because it provides greater access than a drop spine box, the risk of abrasion to the cover of the book is reduced.

drop spine box
A made-to-measure book box, used mainly in preservation, with a spine that falls away on opening to provide access to the spine of the enclosed volume, allowing it to be removed without damage. To see examples, try a keywords search on the term in Google Images.

dry cleaning
In conservation, surface cleaning by mechanical means (brush, eraser, dry cleaning powder, etc.), as opposed to the use of water or chemical agents.

drypoint
A simple intaglio engraving process in which the artist uses a stylus with a fine, sharp steel or diamond point instead of a burin to incise the design directly into the surface of a metal (usually copper) plate. The ragged metal scrapings thrown up on either side of the line (called the "burr") are usually left to hold the ink, printing a soft, fuzzy line in rich, dark black. With successive printings, the burr wears away quickly under the weight of the press, so editions are limited to 50 or fewer prints, unlike an etched plate from which hundreds of fine quality prints can be made. Also refers to the engraving or print made by the process. Click here to see an example by the American artist Mary Cassatt and here to learn more about drypoint, courtesy of the Metropolitan Museum of Art. Also spelled dry point. Compare with etching.

DSL
An abbreviation of digital subscriber line, telecommunication protocols developed in the late 1990s that significantly increase the transmission speed of ordinary telephone lines by employing sophisticated modulation schemes designed to boost the capacity of existing copper wire to transmit digital data, without blocking access to voice services. DSL is sometimes referred to as last-mile technology because it is used only to connect telephone switching stations to homes and offices (end-users), not between switching stations. Level of service depends on the protocol used, ranging from about 128 Kbps to over 8 Mbps.

DTV
An abbreviation of digital television, the broadcasting of moving images and sound as digital signals, rather than the analog signals used for standard television (STV). To receive DTV viewers may use an antenna or subscribe to digital cable or digital satellite service. In the United States, the Federal Communications Commission (FCC) set June 11, 2009 as the date on which terrestrial analog TV broadcasting ceased and was replaced by broadcasting in ATSC digital format. Viewers without digital receivers must now use a converter. By the end of 2009, ten countries had completed the process of turning off analog broadcasting. See also: HDTV.

dual distribution
Federal document titles that are distributed to depository libraries in a choice of either paper or microfiche format under the Federal Depository Library Program (FDLP), with separate item numbers assigned to each format. A selective depository library may choose either format but not both. Also refers to the availability of federal government publications in both electronic and physically tangible formats (print, microfiche, CD-ROM, etc.).

dubbed
A motion picture or video sound track to which dialogue, music, or sound effects have been added. In foreign films, dialogue is often replaced with translation into the language of the country in which the film is distributed, usually in another voice and with loss of lip synchronization. In AACR2, the presence of dubbing is indicated in the note area of the bibliographic description (example: Italian dubbed in English).

Dublin Core (DC)
A standard set of 15 interoperable metadata elements designed to facilitate the description and recovery of document-like resources in a networked environment. The descriptive elements are:

  • Title (name given to the resource)
  • Creator (entity primarily responsible for making the content of the resource)
  • Subject (topic of the content of the resource, typically expressed as keywords, key phrases, or classification codes)
  • Description (abstract, table of contents, free-text account of the content, etc.)
  • Publisher (entity responsible for making the resource available)
  • Contributor (entity responsible for making contributions to the content of the resource)
  • Date (typically associated with the creation or availability of the resource)
  • Type (nature or genre of the content of the resource)
  • Format (physical or digital manifestation of the resource)
  • Identifier (an unambiguous reference to the resource within a given context, such as the URL, ISBN, ISSN, etc.)
  • Source (reference to a resource from which the present resource is derived)
  • Language (the language of the intellectual content of the resource)
  • Relation (reference to a related resource)
  • Coverage (extent or scope of the content of the resource)
  • Rights (information about rights held in and over the resource)

Dublin Core is the result of an international cross-disciplinary consensus achieved through the ongoing efforts of the Dublin Core Metadata Initiative (DCMI), aimed at providing a foundation for standardized bibliographic description of information resources available via the Internet. In 2007, the Dublin Core Metadata Element Set was published by the International Organization for Standardization. Click here to connect to the DCMI homepage.

duck
A plain, strong, closely woven, unsized canvas fabric. Made of cotton or linen, duck is used in bookbinding as a covering material, especially for large, heavy blankbooks and other stationery bindings. It is also used by artists as a surface for painting in oils and acrylics, and in the manufacture of overalls, seat covers, tents, etc.

ductus
In calligraphy, the number of pen strokes required to write a character and the direction and sequence in which they are executed by the scribe. In medieval manuscripts, the ductus of each script was in its time considered by experienced scribes to be the most effortless way of writing it. However, as Marc Drogin notes in Medieval Calligraphy: Its History and Technique (Allanheld & Schram, 1980), two scribes might write a letter differently, or ductus might depend on the letter preceding or following it. On an exemplar, ductus is shown by surrounding the completed letter with numbered arrows indicating the sequence and direction of strokes or by displaying the letter in the process of creation (first stroke, then first and second, and so on, until the final stroke is added). Click here to see ductus illustrated. Plural: ducti. Compare with aspect.

due date
The date of the last day of the loan period, stamped or written by a library staff member on the date due slip affixed to an item when it is checked out at the circulation desk. Fines may be charged for materials returned after the due date if they are not renewed. In the online catalog, the due date may be displayed to indicate the circulation status of an item currently checked out. Synonymous with date due. See also: overdue.

dues
Titles ordered from a publisher that cannot be supplied until additional stock arrives from the printer, usually new books for which stock has not been received or backlisted titles in the process of being reprinted. Such items are usually back ordered.

Also refers to the annual fee that a member of a professional organization, such as the American Library Association (ALA), must pay to keep his or her membership current. Some organizations offer a sliding scale that allows each member to pay an amount corresponding to length of service or level of participation, with students and recent graduates paying the least.

dummy
A single prototype of a book made up of the same number of leaves (usually blank) of the same grade of paper as the final product, trimmed and sewn but usually unbound, to give the binder an idea of bulk and page size and to assist the graphic designer in planning the layout of the dust jacket.

Also refers to the complete layout of every page of a print job, including typeface, type size, and the position of text block, headings, illustrations, captions, etc. See also: shelf dummy.

dummy book
An object made to resemble a bound volume on the outside, but which has no text block or covers that can be opened. Dummy books are also made in the form of thin panels of multiple or single spines, often used for purposes of interior decoration or concealment (see these examples). Synonymous with faux book. Compare with shelf dummy.

dump
A computer operation that copies raw data from one location to another in a system, usually with little or no formatting, for example, the transfer of the contents of memory to a printer or computer screen to display the status of a program at the moment it crashed, useful in diagnosing the nature of a problem.

duodecimo (12mo)
A book, approximately eight inches in height, made by folding a full sheet of book paper to form signatures of 12 leaves (24 pages). See also: folio, quarto, octavo, and sextodecimo.

duotone
An illustration in which the image is printed in two colors, usually black and either dark blue or dark green, a method that allows tint to be applied to a black and white image at considerably less expense than process color. Also refers to the process used to produce such an image. Click here to see a duotone portrait of President Gerald Ford, courtesy of the Ford Presidential Library & Museum. See also: halftone.

duplex
In communications, a channel capable of transmitting signals in both directions (sending and receiving) at the same time. In computer networks, this is usually achieved by using paired wires or by dividing bandwidth into two frequencies. A half-duplex connection is capable of transmitting signals alternately but not simultaneously in either direction, for example, two-way radio. Synonymous with full-duplex. Compare with simplex.

Also refers to a printer attached to a computer or computer network that has the capability to print both sides of a sheet of paper, a means of conserving paper in libraries that allow printing from public access workstations.

duplicate
An additional copy of an item already in a library collection that is not needed. Public libraries often order high-demand items in multiple copies, then weed duplicates as they cease to circulate. Compare with added copy. See also: Duplicates Exchange Union.

In reprography, an exact copy of an original document (either positive or negative) that can be used in place of the original. Also refers to the process of making single or multiple copies of an original document.

duplicate negative
A new negative of a motion picture shot using black and white film, created to preserve the original negative or in numbers for the making of release prints. A duplicate negative can be made from an original print or from a duplicating positive, known as a fine grain master. A composite duplicate negative carries both image and synchronized sound. The dupe made from the original master print is first-generation, the dupe made from the first-generation dupe is second-generation, and so on, with the quality of the image declining with each succeeding generation. Abbreviated dupe negative and dupe neg. Compare with internegative.

duplicate paging
The numbering of pages in duplicate, usually on facing pages, used mainly in books containing parallel texts, for example, a text in translation and the same text in the original language.

duplicate publication
A published article that substantially duplicates another published article without acknowledgment, both articles having one or more authors in common and a substantial amount of identical text. Duplication may be intentional, often to achieve wider dissemination of the content, especially of a specific type of article, such as a policy statement, or inadvertent through multiple submissions of a manuscript to different journals. In some bibliographic databases, such as MEDLINE, the publication type "Duplicate Publication" may be assigned to a citation with or without formal notification from the author(s) or journal editor, often by an indexer who notices substantial similarity.

duplicate record
A bibliographic record that occurs more than once in a library's catalog. In MARC files, this usually occurs when a record is used more than once in OCLC cataloging procedures. When a bibliographic database is created or updated, duplicate records are removed in a batch process known as deduping.

Duplicates Exchange Union (DEU)
An electronic list maintained by the Association for Library Collections and Technical Services (ALCTS) of the American Library Association (ALA) that allows registering libraries of all types to offer duplicate copies for exchange and to request duplicates offered by other libraries free of charge. Libraries requesting materials on exchange are expected to reimburse the originating library for shipping costs. Click here to connect to the DEU homepage.

duplicating positive
A general term for a new positive intermediate print made from the original negative in the preservation copying of a motion picture or in the production of release prints. For motion pictures shot using black and white film, the duplicating positive is called a fine grain master; for color film, it is known as an interpositive.

duplication
The receipt of more copies of a title than the library needs or ordered. This can happen for a variety of reasons, for example, when the catalog is not checked for an existing copy before ordering, when a continuation order is not excluded from an approval plan, or when an approval plan covers materials published simultaneously in the United States and another country. If the duplicate is not returnable, the library may offer it in exchange to another library.

Also, the creation of a surrogate copy of a motion picture, sometimes in a more permanent medium, usually for purposes of preservation. Whenever possible, preservationists work from source material that most closely represents the film as originally shown. When deterioration has occurred, restoration may be required before duplication can proceed.

durability
The degree to which a material retains its physical integrity when subjected to stress, for example, heavy use in the case of some library materials. A durable material, such as the buckram used as a covering in some library bindings, will generally last a relatively long time under conditions of normal use. The opposite of fragility.

dust jacket
The removable paper wrapper on the outside of a hardcover book, usually printed in color and given a glossy finish to market the work to retail customers and protect it from wear and tear. The front of the dust jacket bears the title, the author's full name, and a graphic design. The title also appears on the spine of the jacket, with the author's last name and the publisher's name or symbol. For most trade titles, a promotional blurb written by the publisher appears on the inside flap. The back flap usually provides brief biographical information about the author, which may include a small portrait photograph. The ISBN is printed on the back of the dust jacket, usually in the lower-right-hand corner, following brief quotes from positive reviews of the work. Textbooks, reference books, and sci-tech books are usually sold without a dust jacket.

The first protective paper jacket was provided by a publisher in England in 1833. Since then, dust jacket design has become a highly skilled form of graphic art and a significant factor in the cost of book production. Click here to see the original design for the dust jacket of The Hobbit or There and Back Again by J.R.R. Tolkien, published in 1936 by George Allen & Unwin (Bodleian Library) and here to see a collection of dust jackets for classic crime fiction. In illustrated children's books, the design used on the dust jacket is usually done by the illustrator. Public libraries usually cover the dust jacket with polyester film to protect against abrasion and fading and to enhance visual appeal. In academic libraries, dust jackets are usually removed in processing and used for display or discarded. Abbreviated dj. Synonymous with book jacket and dust cover. Compare with wrappers. See also: sleeve.

DVD
An abbreviation of digital videodisc, a type of optical disk of the same size as a compact disc but with significantly greater recording capacity, partly because it is double-sided. Although DVD requires special equipment for playback, most DVD players can also read CD media. According to the Video Software Dealers Association's weekly VidTrac report, the number of commercial DVD rentals exceeded those of VHS for the first time in June 2003. DVD is now the preferred medium for motion pictures distributed for home use, and the format has superseded VHS in public and academic library collections in the United States. Click here to learn more about DVDs, courtesy of HowStuffWorks. See also: Blu-ray.

DVR
An abbreviation of digital video recorder, an electronic device introduced commercially in 1998, designed to record video in digital format to a hard disk or other storage medium (see this example). The category includes stand-alone set-top boxes, portable media players (PMPs), and software for personal computers that enables video capture and playback to and from disk. Some manufacturers of consumer electronics offer television receivers with DVR hardware and software built into the set. In camcorders, a camera is combined with a DVR. Synonymous with personal video recorder (PVR).

dwell
In tooling, the length of time the heated finishing tool is in contact with the leather or cloth surface being decorated.

dye transfer print
The result of a photographic process in which three separate black and white negatives are made by photographing the original negative through red, green, and blue filters, producing set of separation negatives which are used to expose three continuous-tone film plates called matrices. The matrices are then soaked in water-based organic dyes of complementary color (cyan, magenta, and yellow, respectively), rinsed of excess dye, and rolled in succession, emulsion-side down, into contact with a receiving sheet of gelatin-coated paper, similar to photographic paper but lacking photosensitive silver compounds. The thickness of the matrix image is proportional to the original exposure, as is the amount of dye absorbed by the matrix and subsequently transferred to the print. After the gelatin layer on the paper has absorbed dye from the matrix, the matrix is peeled off, leaving a continuous-tone full-color dye image.

Labor-intensive and expensive to produce, dye transfer prints are valued for their rich, deep colors and archival permanence (more resistant to fading than prints made on light-sensitive chemical papers). Invented in the 1930s before color film became commercially available, the process is becoming a lost art because Kodak ceased manufacturing dye transfer materials in 1993. Click here to see examples, courtesy of the Victoria & Albert Museum, London. Synonymous with dry imbibition print.

dynamic map
A map on which flow lines and/or arrows of variable width are used to indicate the amount and direction of movement (example: migration), exchange (foreign trade), action (military maneuvers), or change in conditions (weather). Click here to see an example showing Jewish emigration from Germany from 1933-1940 (PBS) and here to see a map of the invasion of Italy in September 1943 (Perry-Castañeda Library). Synonymous with flow map.

dystopia
A literary or artistic work set is an unpleasant society or world, usually at a future time or in an imaginary place, in which present tendencies, beliefs, principles, or theories lead to a disagreeable culmination (examples: Brave New World [1932] by Aldous Huxley and 1984 [1949] by George Orwell). Synonymous with anti-utopia. Compare with utopia.


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