data abstraction
data abstraction The principle of defining a
data type in terms of the operations that apply to objects of the type, with the constraint that the values of such objects can be modified and observed only by use of these operations. This application of the general principle of
abstraction leads to the concept of an
abstract data type.
Data abstraction is of very considerable importance in modern programming, especially for the coarse structuring of programs. Such use yields several benefits. The abstract data type provides a natural unit for specification and verification purposes (see
module specification). It provides some basis for high-level design, and is consistent with the principles of
information hiding. The specification of the data type in terms of available operations provides all the information needed to make use of the data type while leaving maximum freedom of implementation, which indeed can be changed if required without affecting the users. There is also the possibility of developing a “library” of useful data abstractions – stacks, queues, etc.
The typical implementation of an abstract data type within a program is by means of a multiprocedure module. This module has local data that can be used to represent a value of the type, and each procedure implements one of the operations associated with the type. The local data of the module can only be accessed by these procedures, so that the user of the data type can only access the operations and has no direct access to the representation. The implementer is therefore free to choose the representation, which remains “invisible” to the users and can be changed if required. Each instance of the abstract data type employs one instance of the local data of the module to represent its value.
Proper support for such multiprocedure modules demands that the concept be recognized by the programming language, which must, for example, allow for the clustering of modules and data and have scope rules reflecting the desired restrictions on access. The first language to provide such support was SIMULA with its CLASS. Many modern languages now offer a similar facility, e.g. the MODULE of Modula and the PACKAGE of Ada. See
package.
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Dictionary of the Khazars as an Epistemological Metaphor.(Critical Essay)
Magazine article from: The Review of Contemporary Fiction; 6/22/1998; ; 700+ words
; ...on Milorad Pavic's Dictionary of the Khazars demonstrate a wide range of ways of approaching...one very quickly loses interest in the Khazars, their history, even their tragic fate...and convincingly as in Dictionary of the Khazars. And the way one has to read the book...
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Dictionary of the Khazars: A Lexicon Novel.
Magazine article from: The Nation; 12/5/1988; ; 700+ words
; There really were Khazars, of Turkish stock, between the Caucasus...court and the military caste of these Khazars converted inexplicably to Judaism. Two...now, most of my romantic notions about Khazars had been borrowed from Arthur Koestler...
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Dictionary of the Khazars as a Khazar Jar.(Critical Essay)
Magazine article from: The Review of Contemporary Fiction; 6/22/1998; ; 700+ words
; ...Jar" from his novel Dictionary of the Khazars, in which a student dream-reader receives...particular passage from Dictionary of the Khazars. "The Khazar Jar" is a parable about...readers are puzzled by Dictionary of the Khazars when it refuses to conform to our predetermined...
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More on the Khazars
Newspaper article from: Jerusalem Post; 2/15/2002; ; 334 words
; 00-00-0000 Headline: More on the Khazars Byline: Elliot Jager Edition; Daily...related topic; includes a long entry on the Khazars, as well as a useful bibliography. There...purportedly between the king of the Khazars and representatives of Islam, Christianity...
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The world of the Khazars; new perspectives.(Brief Article)(Book Review)
Magazine article from: Reference & Research Book News; 11/1/2007; 492 words
; 9789004160422 The world of the Khazars; new perspectives. Ed. by Peter B...epigraphic sources, the conversion of the Khazars to Judaism, Byzantine records, contacts...Halevi, sources from Iran and Armenia, Khazars in Russian nationalist literature and...
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The other Europe in the Middle Ages; Avars, Bulgars, Khazars, and Cumans.(Brief Article)(Book Review)
Magazine article from: Reference & Research Book News; 5/1/2008; 487 words
; ...9789004163898 The other Europe in the Middle Ages; Avars, Bulgars, Khazars, and Cumans. Ed. by Florin Curta. BRILL 2008 492 pages...Others discuss the social and religious milieu, including the Khazars, a tribal kingdom that converted to Judaism in the ninth century...
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Conversations with the Khazars
Newspaper article from: Jerusalem Post; 12/29/1996; ; 689 words
; ...best known for his philosophical conversation-treatise Kuzari, an alleged record of conversations between the king of the Khazars, in the Crimea, and the friend who tries to convince him of the superiority of the Jewish religious approach. Halevi pretended...
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Chaos, Knowledge, and Desire: Narrative Strategies in Dictionary of the Khazars.(Critical Essay)
Magazine article from: The Review of Contemporary Fiction; 6/22/1998; ; 700+ words
; ...emergence of epistemological hypotheses of chaos theory and the narrative organization of Milorad Pavic's Dictionary of the Khazars. The apparent convergence of the narratives developed by chaos theory in mathematical sciences with those of textual postmodernity...
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The Dictionary of the Khazars (excerpts).(Excerpt)
Magazine article from: Serbian Studies; 1/1/2004; 700+ words
; It was after this promise that Dr. Isailo Suk woke and found the key in his mouth. When he stepped out into the street, the afternoon was ailing; a plague of light was blighting the radiance of the sun; an epidemic of boils and rashes spread and erupted across the sky, infecting the clouds, which
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 "Daily Herald (Arlington Heights, IL)")
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Scholar claims to find medieval Jewish capital.(News)
Newspaper article from: Daily Herald (Arlington Heights, IL); 9/21/2008; 700+ words
; ...says he has found the lost capital of the Khazars, a powerful nation that adopted Judaism...once Itil, the Khazar capital. By law Khazars could use flamed bricks only in the capital...truly found the long-lost city, The Khazars were a Turkic tribe that roamed the steppes...
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Khazars
Encyclopedia entry from: Encyclopedia of Russian History
KHAZARS A nomadic Turkic-speaking tribal confederation...an offshoot of the Turk kaghanate, the Khazars established one of the earliest and most...Sea region, during the first phase the Khazars were locked in endless wars against the...
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Kumyks
Encyclopedia entry from: Encyclopedia of World Cultures
...manifesting, however, elements of the languages of the Bulgars and Khazars (ninth and tenth centuries) and the Oghuz Turks (eleventh...and those of the Sabirs, the Barsils, the Bulgars, the Khazars, the Kipchaks, and others. In the eighteenth and nineteenth...
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Kievan Rus
Book article from: The Columbia Encyclopedia, Sixth Edition
...the Eastern Slavs and freed them from the suzerainty of the Khazars . His successors were Igor or Ihor (reigned 912-45) and...Under Olga's son, Sviatoslav or Svyatoslav (d. 972), the Khazars were crushed, and Kievan power was extended to the lower Volga...
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Polyane
Encyclopedia entry from: Encyclopedia of Russian History
...western-most military outpost and a commercial center for the Khazars. During the late ninth century, the Rus prince Oleg (legendary...their pre-Christian religious practices. See also: igor; khazars; kievan rus; oleg; primarychronicle; vikings bibliography...
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Torky
Encyclopedia entry from: Encyclopedia of Russian History
...Sea steppe region. In the late ninth century, joined by the Khazars, they expelled the Pechenegs from the Volga-Ural area and...the holder of the title of Grand Prince of Kiev. See also: khazars; kievan rus; polovtsy bibliography Golden, Peter B. (1990...
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