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85
Relational Databases for Querying XML Documents: Limitations and Opportunities
, 1999
"... XML is fast emerging as the dominant standard for representing data in the World Wide Web. Sophisticated query engines that allow users to effectively tap the data stored in XML documents will be crucial to exploiting the full power of XML. While there has been a great deal of activity recently prop ..."
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Cited by 391 (10 self)
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XML is fast emerging as the dominant standard for representing data in the World Wide Web. Sophisticated query engines that allow users to effectively tap the data stored in XML documents will be crucial to exploiting the full power of XML. While there has been a great deal of activity recently proposing new semistructured data models and query languages for this purpose, this paper explores the more conservative approach of using traditional relational database engines for processing XML documents conforming to Document Type Descriptors (DTDs). To this end, we have developed algorithms and implemented a prototype system that converts XML documents to relational tuples, translates semistructured queries over XML documents to SQL queries over tables, and converts the results to XML. We have qualitatively evaluated this approach using several real DTDs drawn from diverse domains. It turns out that the relational approach can handle most (but not all) of the semantics of semistructured queries over XML data, but is likely to be effective only in some cases. We identify the causes for these limitations and propose certain extensions to the relational
Extending the Database Relational Model to Capture More Meaning
 ACM Transactions on Database Systems
, 1979
"... During the last three or four years several investigators have been exploring “semantic models ” for formatted databases. The intent is to capture (in a more or less formal way) more of the meaning of the data so that database design can become more systematic and the database system itself can beha ..."
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Cited by 242 (1 self)
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During the last three or four years several investigators have been exploring “semantic models ” for formatted databases. The intent is to capture (in a more or less formal way) more of the meaning of the data so that database design can become more systematic and the database system itself can behave more intelligently. Two major thrusts are clear: (I) the search for meaningful units that are as small as possibleatomic semantics; (2) the search for meaningful units that are larger than the usual nary relationmolecular semantics. In this paper we propose extensions to the relational model to support certain atomic and molecular semantics. These extensions represent a synthesis of many ideas from the published work in semantic modeling plus the introduction of new rules for insertion, update, and deletion, as well as new algebraic operators.
Logic and databases: a deductive approach
 ACM Computing Surveys
, 1984
"... The purpose of this paper is to show that logic provides a convenient formalism for studying classical database problems. There are two main parts to the paper, devoted respectively to conventional databases and deductive databases. In the first part, we focus on query languages, integrity modeling ..."
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Cited by 143 (2 self)
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The purpose of this paper is to show that logic provides a convenient formalism for studying classical database problems. There are two main parts to the paper, devoted respectively to conventional databases and deductive databases. In the first part, we focus on query languages, integrity modeling and maintenance, query optimization, and data
Fuzzy functional dependencies and lossless join decomposition of fuzzy relational database systems
 ACM Transactions on Database Systems
, 1988
"... This paper deals with the application of fuzzy logic in a relational database environment with the objective of capturing more meaning of the data. It is shown that with suitable interpretations for the fuzzy membership functions, a fuzzy relational data model can be used to represent ambiguities in ..."
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Cited by 73 (0 self)
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This paper deals with the application of fuzzy logic in a relational database environment with the objective of capturing more meaning of the data. It is shown that with suitable interpretations for the fuzzy membership functions, a fuzzy relational data model can be used to represent ambiguities in data values as well as impreciseness in the association among them. Relational operators for fuzzy relations have been studied, and applicability of fuzzy logic in capturing integrity constraints has been investigated. By introducing a fuzzy resemblance measure EQUAL for comparing domain values, the definition of classical functional dependency has been generalized to fuzzy functional dependency (ffd). The implication problem of ffds has been examined and a set of sound and complete inference axioms has been proposed. Next, the problem of lossless join decomposition of fuzzy relations for a given set of fuzzy functional dependencies is investigated. It is proved that with a suitable restriction on EQUAL, the design theory of a classical relational database with functional dependencies can be extended to fuzzy relations satisfying fuzzy functional dependencies.
A consideration on normal form of notnecessarilynormalized relation in the relational data model
, 1977
"... In this paper definitions of unnormalized relation, functional dependency on it and Normal Form are presented. The Normal Form plays a key role in our relational data model in which unnormalized relations are admitted as does the Third Normal Form of Codd in the data model of normalized relation. Pr ..."
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Cited by 68 (0 self)
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In this paper definitions of unnormalized relation, functional dependency on it and Normal Form are presented. The Normal Form plays a key role in our relational data model in which unnormalized relations are admitted as does the Third Normal Form of Codd in the data model of normalized relation. Properties pertaining to Normal Form are discussed emphasizing comparison with 3NF along with analysis of some typical examples. Similarity and dissimilarity between new functional dependency and Fagin's multivalued dependency are also discussed and presented in the form of proposition. 1. INTRODUCTION 2. AN EXTENSION OF F!lNCTIONAL DEPENDENCY Codd proposed a relational model of data in his earlier paper [l] and developed his idea on normalization of relational data model in his succeeding oaoers 12 and 41. He defined three tvoes of normal
Quasiinverses of schema mappings
 In Proceedings of the ACM Symposium on Principles of Database Systems (PODS
, 2007
"... Schema mappings are highlevel specifications that describe the relationship between two database schemas. Two operators on schema mappings, namely the composition operator and the inverse operator, are regarded as especially important. Progress on the study of the inverse operator was not made unti ..."
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Cited by 56 (8 self)
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Schema mappings are highlevel specifications that describe the relationship between two database schemas. Two operators on schema mappings, namely the composition operator and the inverse operator, are regarded as especially important. Progress on the study of the inverse operator was not made until very recently, as even finding the exact semantics of this operator turned out to be a fairly delicate task. Furthermore, this notion is rather restrictive, since it is rare that a schema mapping possesses an inverse. In this article, we introduce and study the notion of a quasiinverse of a schema mapping. This notion is a principled relaxation of the notion of an inverse of a schema mapping; intuitively, it is obtained from the notion of an inverse by not differentiating between instances that are equivalent for dataexchange purposes. For schema mappings specified by sourcetotarget tuplegenerating dependencies (st tgds), we give a necessary and sufficient combinatorial condition for the existence of a quasiinverse, and then use this condition to obtain both positive and negative results about the existence of quasiinverses. In particular, we show that every LAV (localasview) schema mapping has a quasiinverse, but that there are schema mappings specified by full st tgds that have no quasiinverse. After this, we study the language needed to express quasiinverses of schema mappings
Logical and algorithmic properties of conditional independence and graphical models
 THE ANNALS OF STATISTICS
, 1993
"... ..."
A New Normal Form for Nested Relations
 ACM Transactions on Database Systems
, 1987
"... We consider nested relations whose schemes are structured as trees, called scheme trees, and introduce a normal form for such relations, called the nested normal form. Given a set of attributes U, and a set of multivalued dependencies (MVDs) M over these attributes, we present an algorithm to obtain ..."
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Cited by 52 (2 self)
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We consider nested relations whose schemes are structured as trees, called scheme trees, and introduce a normal form for such relations, called the nested normal form. Given a set of attributes U, and a set of multivalued dependencies (MVDs) M over these attributes, we present an algorithm to obtain a nested normal form decomposition of U with respect to M. Such a decomposition has several desirable properties, such as explicitly representing a set of full and embedded MVDs implied by M, and being a faithful and nonredundant representation of U. Moreover, if the given set of MVDs is conflict free, then the nested normal form decomposition is also dependency preserving. Finally, we show that if M is conflict free, then the set of roottoleaf paths of scheme trees in nested normal form decomposition is precisely the unique 4NF decomposition [Fa, L2] of U with respect to M. 1. Introduction A relational database [Co] is a collection of relations where each relation is at least in First ...
Computing With FirstOrder Logic
, 1995
"... We study two important extensions of firstorder logic (FO) with iteration, the fixpoint and while queries. The main result of the paper concerns the open problem of the relationship between fixpoint and while: they are the same iff ptime = pspace. These and other expressibility results are obtaine ..."
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Cited by 52 (13 self)
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We study two important extensions of firstorder logic (FO) with iteration, the fixpoint and while queries. The main result of the paper concerns the open problem of the relationship between fixpoint and while: they are the same iff ptime = pspace. These and other expressibility results are obtained using a powerful normal form for while which shows that each while computation over an unordered domain can be reduced to a while computation over an ordered domain via a fixpoint query. The fixpoint query computes an equivalence relation on tuples which is a congruence with respect to the rest of the computation. The same technique is used to show that equivalence of tuples and structures with respect to FO formulas with bounded number of variables is definable in fixpoint. Generalizing fixpoint and while, we consider more powerful languages which model arbitrary computation interacting with a database using a finite set of FO queries. Such computation is modeled by a relational machine...
An InformationTheoretic Approach to Normal Forms for Relational and XML Data
 In PODS
, 2003
"... Normalization as a way of producing good database designs is a wellunderstood topic. ..."
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Cited by 44 (8 self)
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Normalization as a way of producing good database designs is a wellunderstood topic.