Results 271 to 280 of about 39,846 (313)
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Watermarking Relational Databases
2002We enunciate the need for watermarking database relations to deter their piracy, identify the unique characteristics of relational data which pose new challenges for watermarking, and provide desirable properties of a watermarking system for relational data.
Rakesh Agrawal 0001, Jerry Kiernan
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Equivalence of relational database schemes
Proceedings of the eleventh annual ACM symposium on Theory of computing - STOC '79, 1979We investigate the question of when two database schemes embody the same information. We argue that this question reduces to the equivalence of the sets of fixed points of the project-join mappings associated with the two database schemes in question.
Catriel Beeri +3 more
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Assumptions in relational database theory
Proceedings of the 1st ACM SIGACT-SIGMOD symposium on Principles of database systems - PODS '82, 1982Many results in relational database theory on the structure of dependencies, query languages, and databases in general have now been established. However, neither (a) the reliance of these results on various assumptions, nor (b) the desirability or reasonableness of these assumptions themselves have been closely examined.
ATZENI, Paolo, PARKER DS
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Answering queries in relational databases
ACM SIGMOD Record, 1983This paper concerns query answering in relational databases. We assume a universe U of attributes and a set of values associated with each attribute. A database scheme is a given collection R = {1, 2, ..., n} of subsets of U, called relation schemes. A query in R is any subset of U. We call "context" any joinable subset of R.
D'ATRI, ALESSANDRO +2 more
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Metaprogramming for Relational Databases
2004For systems that share enough structural and functional commonalities, reuse in schema development and data manipulation can be achieved by defining problem-oriented languages. Such languages are often called domainspecific, because they introduce powerful abstractions meaningful only within the domain of observed systems.
Jernej Kovse +2 more
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On decomposition of relational databases
23rd Annual Symposium on Foundations of Computer Science (sfcs 1982), 1982A central issue in relational database theory is that of decomposition. It has been agreed that decompositions should be injective, so as not to lose information, and surjective, so they decompose a relation into independent components. Injectiveness and surjectiveness are in general second-order notions.
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IEEE Transactions on Knowledge and Data Engineering, 1993
The concept of an inductive relation is introduced, as a natural development of other forms of intentional information, such as views and relations defined deductively. A class of top-down methods for computing such inductive relations is analyzed. Major problems produced by recursive and interdependent relations are considered. >
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The concept of an inductive relation is introduced, as a natural development of other forms of intentional information, such as views and relations defined deductively. A class of top-down methods for computing such inductive relations is analyzed. Major problems produced by recursive and interdependent relations are considered. >
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Compiling subsumption to relational databases
Intelligenza Artificiale: The international journal of the AIxIA, 2013We investigate on the possibility of transforming concepts in Description Logics into relational databases and queries in such a way that subsumption between the original concepts can be decided as query answering over a database. For the positive results, we show a translation of -concepts into pairs (database, query) such that, in order to decide ...
Eufemia Tinelli +2 more
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Incomplete Information in Relational Databases
Journal of the ACM, 1984ABSTRACT This paper concerns the semantics of Codd's relational model of data. Formulated are precise conditions that should be satisfied in a semantically meaningful extension of the usual relational operators, such as projection, selection, union, and join, from operators on relations to operators on tables with “null values” of various kinds ...
Tomasz Imielinski, Witold Lipski Jr.
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A Virtual XML Database Engine for Relational Databases
2003While XML is emerging as the universal format for publishing and exchanging data on the Web, most business data is still stored and maintained in relational DBMSs. To enable eBusiness database applications, Web access to the legacy data managed by DBMSs needs to be provided.
Chengfei Liu +3 more
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