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Design by example for SQL table definitions with functional dependencies
 THE VLDB JOURNAL
, 2011
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The implication problem of data dependencies over SQL table definitions: axiomatic, algorithmic and logical characterizations
"... We investigate the implication problem for classes of data dependencies over SQL table definitions. Under Zaniolo’s “no information ” interpretation of null markers we establish an axiomatization and algorithms to decide the implication problem for the combined class of functional and multivalued de ..."
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We investigate the implication problem for classes of data dependencies over SQL table definitions. Under Zaniolo’s “no information ” interpretation of null markers we establish an axiomatization and algorithms to decide the implication problem for the combined class of functional and multivalued dependencies in the presence of NOT NULL constraints. The resulting theory subsumes three previously orthogonal frameworks. We further show that the implication problem of this class is equivalent to that in a propositional fragment of Cadoli and Schaerf ’s family of paraconsistent S3 logics. In particular, S is the set of variables that correspond to attributes declared NOT NULL. We also show how our equivalences for multivalued dependencies can be extended to Delobel’s class of full firstorder hierarchical decompositions, and the equivalences for functional dependencies can be extended to arbitrary Boolean dependencies. These dualities allow us to transfer several findings from the propositional fragments to the corresponding classes of data dependencies, and vice versa. We show that our results also apply to Codd’s null interpretation “value unknown at present”, but not to Imielinski’s orrelations utilizing Levene and Loizou’s weak possible world semantics. Our findings establish NOT NULL constraints as an effective mechanism to balance not only the certainty in database relations but also the expressiveness with the efficiency of entailment relations. They also control the degree by which the implication of data dependencies over total relations is soundly approximated
Chase and Axioms for PC Queries and Dependencies
, 1998
"... This report is the extended version of [PT99] and while they are some overlapping parts (mainly the results) we don't repeat here some of the examples given in [PT99], even though we frequently refer to them. The overview of this report is as follows. In section 2 we present some aspects of our ..."
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Cited by 5 (5 self)
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This report is the extended version of [PT99] and while they are some overlapping parts (mainly the results) we don't repeat here some of the examples given in [PT99], even though we frequently refer to them. The overview of this report is as follows. In section 2 we present some aspects of our internal framework, called CoDi
Exploiting Functional Dependence in Query Optimization
, 2000
"... I authorize the University of Waterloo to lend this thesis to other institutions or individuals for the purpose of scholarly research. I further authorize the University of Waterloo to reproduce this thesis by photocopying or by other means, in total or in part, at the request of other institutions ..."
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I authorize the University of Waterloo to lend this thesis to other institutions or individuals for the purpose of scholarly research. I further authorize the University of Waterloo to reproduce this thesis by photocopying or by other means, in total or in part, at the request of other institutions or individuals for the purpose of scholarly research. iii The University of Waterloo requires the signatures of all persons using or photocopying this thesis. Please sign below, and give address and date. Functional dependency analysis can be applied to various problems in query optimization: selectivity estimation, estimation of (intermediate) result sizes, order optimization (in particular sort avoidance), cost estimation, and various problems in the area of semantic query optimization. Dependency analysis in an ansi sql relational model, however, is made complex due to the existence of null values, threevalued logic, outer joins, and duplicate rows. In this thesis we define the notions of strict and lax functional dependencies, strict and lax equivalence constraints, and null constraints, which capture both a
Firstorder Logic Characterization of Program Properties
 IEEE Transaction on Knowledge and Data Engineering, Vol
, 1994
"... A program is firstorder reducible (FOreducible) with respect to (wrt) a set of integrity constraints if there exists a firstorder theory T such that the set of models for T is exactly the set of intended models for the program wrt all possible EDB's. In this case, we say that P is FOreduci ..."
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A program is firstorder reducible (FOreducible) with respect to (wrt) a set of integrity constraints if there exists a firstorder theory T such that the set of models for T is exactly the set of intended models for the program wrt all possible EDB's. In this case, we say that P is FOreducible to T wrt IC. For FOreducible programs, it is possible to characterize, using firstorder logic implications, properties of programs that are related to all possible EDB's as in the database context. These properties include, among others, containment of programs, independence of updates wrt queries and integrity constraints, and characterization and implication of integrity constraints in programs, all of which have no known proof procedures. Therefore, many important problems formalized in a nonstandard logic can be dealt with using the rich reservoir of firstorder theoremproving tools, provided that the program is FOreducible. The following classes of programs are shown to be FOreduc...
Inference Rules for Nested Functional Dependencies
, 1999
"... Functional dependencies add semantics to a database schema# and are useful for studying vari# ous problems# such as database design# query optimization and how dependencies are carried into a view. In the context of a nested relational model# these dependencies can be extended by using path expressi ..."
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Functional dependencies add semantics to a database schema# and are useful for studying vari# ous problems# such as database design# query optimization and how dependencies are carried into a view. In the context of a nested relational model# these dependencies can be extended by using path expressions instead of attribute names# resulting in a class of dependencies that we call nested functional dependencies #NFDs#. NFDs de#ne a natural class of dependencies in complex data struc# tures# in particular they allow the speci#cation of many useful intra# and inter#set dependencies #i.e.# dependencies that are local to a set and dependencies that require consistency between sets#. Such constraints cannot be captured by existing notions of functional# multi#valued# or join dependencies. This paper presents the de#nition of NFDs and gives their meaning by translation to logic. It then presents a sound and complete set of eight inference rules for NFDs# and discusses approaches to handling th...
G.: The ICSFORTH SWIM: A Powerful Semantic Web Integration Middleware. Submitted for publication (2003
"... Abstract. Semantic Web (SW) technology aims to facilitate the integration of legacy data sources spread worldwide. Despite the plethora of SW languages (e.g., RDF/S, DAML+OIL, OWL) recently proposed for capturing data semantics, the vast majority of legacy sources still rely on relational databases ..."
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Abstract. Semantic Web (SW) technology aims to facilitate the integration of legacy data sources spread worldwide. Despite the plethora of SW languages (e.g., RDF/S, DAML+OIL, OWL) recently proposed for capturing data semantics, the vast majority of legacy sources still rely on relational databases (RDB) published on the Web or corporate intranets as virtual XML. In this paper, we advocate a Datalog framework for mediating highlevel queries to relational and/or XML sources using community ontologies expressed in a SW language such as RDF/S. We describe the architecture and the reasoning services of our SW integration middleware, called SWIM, and we present the main design choices and techniques for supporting powerful mappings between di erent data models, as well as, reformulation and optimization of queries expressed against mediation schemas and views. 1
Value Invention in Data Exchange
"... The creation of values to represent incomplete information, often referred to as value invention, is central in data exchange. Within schema mappings, Skolem functions have long been used for value invention as they permit a precise representation of missing information. Recent work on a powerful m ..."
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The creation of values to represent incomplete information, often referred to as value invention, is central in data exchange. Within schema mappings, Skolem functions have long been used for value invention as they permit a precise representation of missing information. Recent work on a powerful mapping language called secondorder tuple generating dependencies (SO tgds), has drawn attention to the fact that the use of arbitrary Skolem functions can have negative computational and programmatic properties in data exchange. In this paper, we present two techniques for understanding when the Skolem functions needed to represent the correct semantics of incomplete information are computationally wellbehaved. Specifically, we consider when the Skolem functions in secondorder (SO) mappings have a firstorder (FO) semantics and are therefore programmatically and computationally more desirable for use in practice. Our first technique, linearization, significantly extends the Nash, Bernstein and Melnik unskolemization algorithm, by understanding when the sets of arguments of the Skolem functions in a mapping are related by set inclusion. We show that such a linear relationship leads to mappings that have FO semantics and are expressible in popular mapping languages including sourcetotarget tgds and nested tgds. Our second technique uses source semantics, specifically functional dependencies (including keys), to transform SO mappings into equivalent FO mappings. We show that our algorithms are applicable to a strictly larger class of mappings than previous approaches, but more importantly we present an extensive experimental evaluation that quantifies this difference (about 78 % improvement) over an extensive schema mapping benchmark and illustrates the applicability of our results on real mappings.