Characterization of desirable properties of general database decompositions

Hegner, Stephen J.

doi:10.1007/bf01556353

Cited by 7 publications

(3 citation statements)

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“…In [8], the connection between decompositions of database schemata and commuting congruences is investigated thoroughly. Summary 2.2 (The order-based framework).…”

Section: Fig 3 Relative Viewsmentioning

confidence: 99%

The Relative Complexity of Updates for a Class of Database Views

Hegner

2004

Lecture Notes in Computer Science

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Abstract. It is well known that the complexity of testing the correctness of an arbitrary update to a database view can be far greater than the complexity of testing a corresponding update to the main schema. However, views are generally managed according to some protocol which limits the admissible updates to a subset of all possible changes. The question thus arises as to whether there is a more tractable relationship between these two complexities in the presence of such a protocol. In this paper, this question is answered in the affirmative for closed update strategies, which are based upon the constant-complement approach of Bancilhon and Spyratos. Working within a very general framework which is independent of any particular data model, but which recaptures relational schemata constrained by so-called equality-generating dependencies (EGDs), (which include functional dependencies (FDs)), it is shown that the complexity of testing the correctness of a view update which follows a closed update strategy is no greater than that of testing a corresponding update to the main schema. In particular, if the main schema is relational and constrained by FDs, then there exists a set of FDs on the view, against which any candidate update may be tested for correctness. This holds even though the entire view may not be finitely axiomatizable, much less constrained by FDs alone.

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“…In [8], the connection between decompositions of database schemata and commuting congruences is investigated thoroughly. Summary 2.2 (The order-based framework).…”

Section: Fig 3 Relative Viewsmentioning

confidence: 99%

The Relative Complexity of Updates for a Class of Database Views

Hegner

2004

Lecture Notes in Computer Science

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“…In [Heg93], the connection between decompositions of database schemata and commuting congruences is investigated thoroughly.…”

Section: The Classical Results In the Set-based Frameworkmentioning

confidence: 99%

“…It is the condition on a complementary pair which ensures that constantcomplement update strategies are independent of the state of the complement [Heg04a, 3.10]. In addition, commuting congruences play a key rôle in the characterization of "desirable" properties of decompositions which are related to the classical notion of acyclic schemata [Heg93].…”

Section: Fully Commuting Views and Meet Complementsmentioning

confidence: 99%

The complexity of embedded axiomatization for a class of closed database views

Hegner

2006

Ann Math Artif Intell

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It is well known that the complexity of testing the correctness of an arbitrary update to a database view can be far greater than the complexity of testing a corresponding update to the main schema. However, views are generally managed according to some protocol which limits the admissible updates to a subset of all possible changes. The question thus arises as to whether there is a more tractable relationship between these two complexities in the presence of such a protocol. In this paper, this question is addressed for closed update strategies, which are based upon the constant-complement approach of Bancilhon and Spyratos. The approach is to address a more general question -that of characterizing the complexity of axiomatization of views, relative to the complexity of axiomatization of the main schema. For schemata constrained by denial or consistency constraints, that is, statements which rule out certain situations, such as the equalitygenerating dependencies (EGDs) or, more specifically, the functional dependencies (FDs) of the relational model, a broad and comprehensive result is obtained in a very general framework which is not tied to the relational model in any way. It states that every such schema is governed by an equivalent set of constraints which embed into the component views, and which are no more complex than the original set. For schemata constrained by generating dependencies, of which tuple-generating dependencies (TGDs) in general and, more specifically, both join dependencies (JDs) and inclusion dependencies (INDs) are examples within the relational model, a similar result is obtained, but only within a context known as meet-uniform decompositions, which fails to recapture some important situations.To address the all-important case of relational schemata constrained by both FDs and INDs, a hybrid approach is also developed, in which the general theory regarding denial constraints is blended with a focused analysis of a special but very practical subset of the INDs known as fanout-free unary inclusion dependencies (fanout-free UINDs), to obtain results parallel to the above-mentioned cases: every such schema is governed by an equivalent set of constraints which embed into the component views, and which are no more complex than the original set. In all cases, the question of view update complexity is then answered via a corollary to this main result. † Parts of this paper are based upon work reported in [Heg04b] 1

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Uniqueness of Update Strategies for Database Views

Hegner

2002

Lecture Notes in Computer Science

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Characterization of desirable properties of general database decompositions

Cited by 7 publications

References 28 publications

The Relative Complexity of Updates for a Class of Database Views

The Relative Complexity of Updates for a Class of Database Views

The complexity of embedded axiomatization for a class of closed database views

Uniqueness of Update Strategies for Database Views

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