Uniqueness of Update Strategies for Database Views

Hegner, Stephen J.

doi:10.1007/3-540-45758-5_15

Cited by 5 publications

(16 citation statements)

References 11 publications

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“…Summary 2.1 recaps the essential ideas of closed update strategies within the original set-based framework. Thus, it provides the essence of the framework of [1], although it is recast within the formalism of [2] [3]. Summary 2.2 sketches the key ideas developed in [2] [3] which are necessary to extend the set-based ideas to the order-based context.…”

Section: An Overview Of Existing Workmentioning

confidence: 99%

“…While every effort has been made to keep this paper self contained, it may nevertheless be necessary to consult [2] and/or [3] to resolve detailed technical issues. Also, while the general theory is not attached to any particular data model, numerous examples are taken from the classical relational theory.…”

Section: An Overview Of Existing Workmentioning

confidence: 99%

“…The theory developed in [2] and [3] provides a systematic extension to the results outlined in Summary 2.1 above to the order-based setting. A order schema D is taken to be a partially ordered set (poset) §…”

Section: Fig 3 Relative Viewsmentioning

confidence: 99%

“…In more recent work, [2], [3], it is shown that by augmenting this basic framework with natural order structure, true uniqueness for so-called order-based updates may be obtained, in the sense that there is but one way to represent an update to the view in terms of an update to the main schema, regardless of the choice of complement. (Orderbased updates are those which are realizable as a sequence of insertions and deletions.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, the work of [2] and [3] is continued with an initial investigation of the complexity of determining whether a proposed view update is valid. This all updates under closed update strategies in an order-based framework reflect uniquely back to the main view.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: An Overview Of Existing Workmentioning

confidence: 99%

Section: An Overview Of Existing Workmentioning

confidence: 99%

Section: Fig 3 Relative Viewsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Relative Complexity of Updates for a Class of Database Views

Hegner

2004

Lecture Notes in Computer Science

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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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Comparative study of view update algorithms in rational choice theory

Delhibabu¹

2014

Appl Intell

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The dynamics of belief and knowledge is one of the major components of any autonomous system that should be able to incorporate new pieces of information. We show that knowledge base dynamics has interesting connection with kernel change via hitting set and abduction. The approach extends and integrates standard techniques for efficient query answering and integrity checking. The generation of hitting set is carried out through a hyper tableaux calculus and magic set that is focused on the goal of minimality. Many different view update algorithms have been proposed in the literature to address this problem. The present paper provides a comparative study of view update algorithms in rational approach. ⋆ This paper extends work from Delhibabu [34] and Mayol [83] Our knowledge base dynamics is defined in two parts: an immutable part (formulae) and updatable part (literals) (for definition and properties see works of Nebel [88] and Segerberg [98]). Knowledge bases have a set of integrity constraints (see the definitions in later section). In the case of finite knowledge bases, it is sometimes hard to see how the update relations should be modified to accomplish certain knowledge base updates.Example 1. Consider a database with an (immutable) rule that a staff member is a person who is currently working in a research group under a chair. Additional (updatable) facts are that matthias and gerhard are group chairs, and delhibabu and aravindan are staff members in group info1. Our first integrity constraint (IC) is that each research group has only one chair ie. ∀x, y, z (y=x) ← group chair(x,y) ∧ group chair(x,z). Second integrity constraint is that a person can be a chair for only one research group ie. ∀x, y, z (y=z)← group chair(y,x) ∧ group chair(z,x).Immutable part: staff chair(X,Y)← staff group(X,Z),group chair(Z,Y). Updatable part: group chair(infor1,matthias)← group chair(infor2,gerhard)← staff group(delhibabu,infor1)← staff group(aravindan,infor1)← Suppose we want to update this database with the information, staff chair(aravindan,gerhard); From the immutable part, we can deduce that this can be achieved by asserting staff group(aravindan,Z) group chair(Z,gerhard)If we are restricted to definite clauses, there are three plausible ways to do this: first case is, aravindan and gerhard belong to infor1, i.e, staff group(aravindan,-info1) group chair(info1,gerhard). We need to delete both base facts group chair-(infor1,matthias)← and group chair(infor2,gerhard)←, because our first IC as well as second IC would be violated otherwise. In order to change the view, we need to insert group chair(infor1,gerhard)← as a base fact. Assume that we have an algorithm that deletes the base facts staff group(delhibabu,infor1)← from the database. But, no rational person will agree with such an algorithm, because the fact staff group(delhibabu,infor1)← is not "relevant" to the view atom.Second case, aravindan and gerhard belong to infor2, that is staff group(aravindan,info2) group chair(info2,gerhard). Simply, insert the new fact ...

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Uniqueness of Update Strategies for Database Views

Cited by 5 publications

References 11 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

Comparative study of view update algorithms in rational choice theory

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