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Data independence

About: Data independence is a research topic. Over the lifetime, 434 publications have been published within this topic receiving 12808 citations.


Papers
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Journal ArticleDOI
E. F. Codd1
TL;DR: In this article, a model based on n-ary relations, a normal form for data base relations, and the concept of a universal data sublanguage are introduced, and certain operations on relations are discussed and applied to the problems of redundancy and consistency in the user's model.
Abstract: Future users of large data banks must be protected from having to know how the data is organized in the machine (the internal representation). A prompting service which supplies such information is not a satisfactory solution. Activities of users at terminals and most application programs should remain unaffected when the internal representation of data is changed and even when some aspects of the external representation are changed. Changes in data representation will often be needed as a result of changes in query, update, and report traffic and natural growth in the types of stored information.Existing noninferential, formatted data systems provide users with tree-structured files or slightly more general network models of the data. In Section 1, inadequacies of these models are discussed. A model based on n-ary relations, a normal form for data base relations, and the concept of a universal data sublanguage are introduced. In Section 2, certain operations on relations (other than logical inference) are discussed and applied to the problems of redundancy and consistency in the user's model.

4,990 citations

Journal ArticleDOI
TL;DR: The analysis of cross-classified data: Independence, quasi-independence, and Interactions in Contingency Tables with or without Missing Entries as mentioned in this paper is an example of such a model.
Abstract: (1968). The Analysis of Cross-Classified Data: Independence, Quasi-Independence, and Interactions in Contingency Tables with or without Missing Entries. Journal of the American Statistical Association: Vol. 63, No. 324, pp. 1091-1131.

469 citations

Journal ArticleDOI
TL;DR: In this article, the authors proposed an alternative based on a permanence of updating ratios, which guarantees all limit conditions even in the presence of complex data interdependence, and extended the recombination formula to any number n of data events.
Abstract: Consider the assessment of any unknown event A through its conditional probability P(A | B,C) given two data events B, C of different sources. Each event could involve many locations jointly, but the two data events are assumed such that the probabilities P(A | B) and P(A | C) can be evaluated. The challenge is to recombine these two partially conditioned probabilities into a model for P(A | B,C) without having to assume independence of the two data events B and C. The probability P(A | B,C) is then used for estimation or simulation of the event A. In presence of actual data dependence, the combination algorithm provided by the traditional conditional independence hypothesis is shown to be nonrobust leading to various inconsistencies. An alternative based on a permanence of updating ratios is proposed, which guarantees all limit conditions even in presence of complex data interdependence. The resulting recombination formula is extended to any number n of data events and a paradigm is offered to introduce formal data interdependence.

272 citations

Journal ArticleDOI
Peter Dadam1, K. Kuespert1, F. Andersen1, H. Blanken1, R. Erbe1 
15 Jun 1986
TL;DR: This paper reports on a 3-year effort to design and prototype a DBMS to support a generalized relational data model, called extended NF2 (Non First Normal Form) data model which treats flat relations, lists, and hierarchical structures in a uniform way.
Abstract: Recently, extensions for relational database management systems (DBMS) have been proposed to support also hierarchical structures (complex objects). These extensions have been mainly implemented on top of an existing DBMS. Such an approach leads to many disadvantages not only from the conceptual point of view but also from performance aspects. Thus paper reports on a 3-year effort to design and prototype a DBMS to support a generalized relational data model, called extended NF2 (Non First Normal Form) data model which treats flat relations, lists, and hierarchical structures in a uniform way. The logical data model, a language for this model, and alternatives for storage structures to implement generalized relations are presented and discussed.

258 citations

Book ChapterDOI
07 Nov 2004
TL;DR: This paper addresses the problem of building scalable semantic overlay networks by separating a logical layer, the semantic overlay for managing and mapping data and metadata schemas, from a physical layer consisting of a structured peer-to-peer overlay network for efficient routing of messages.
Abstract: This paper addresses the problem of building scalable semantic overlay networks. Our approach follows the principle of data independence by separating a logical layer, the semantic overlay for managing and mapping data and metadata schemas, from a physical layer consisting of a structured peer-to-peer overlay network for efficient routing of messages. The physical layer is used to implement various functions at the logical layer, including attribute-based search, schema management and schema mapping management. The separation of a physical from a logical layer allows us to process logical operations in the semantic overlay using different physical execution strategies. In particular we identify iterative and recursive strategies for the traversal of semantic overlay networks as two important alternatives. At the logical layer we support semantic interoperability through schema inheritance and Semantic Gossiping. Thus our system provides a complete solution to the implementation of semantic overlay networks supporting both scalability and interoperability.

244 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20212
20204
20197
201810
20175
20168