Journal ArticleDOI
Minimizing function-free recursive inference rules
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TLDR
It is shown that testing for minimality is, in general, undecidable, and an efficient algorithm for a useful class of recursive rules is presented, and it is used to transform a recursive definition to a minimal recursive definition.Abstract:
Recursive inference rules arise in recursive definitions in logic programming systems and in database systems with recursive query languages. Let D be a recursive definition of a relation t. D is considered minimal if for any predicate p in a recursive rule in D, p must appear in a recursive rule in any definition of t. It is shown that testing for minimality is, in general, undecidable. However, an efficient algorithm for a useful class of recursive rules is presented, and it is used to transform a recursive definition to a minimal recursive definition. Evaluating the minimized definition avoids redundant computation without the overhead of caching intermediate results and run-time checking for duplicate goals.read more
Citations
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Proceedings ArticleDOI
Query optimization by simulated annealing
Yannis Ioannidis,Eugene Wong +1 more
TL;DR: A query optimization algorithm based on simulated annealing, which is a probabilistic hill climbing algorithm for optimizing complex non-recursive queries that arise in the study of linear recursion.
Proceedings Article
Undecidable Optimization Problems for Database Logic Programs
TL;DR: In this article, it was shown that the problem of deciding whether a given Datalog program is bounded is undecidable, even for linear programs (i.e., programs in which each rule contains at most one occurrence of a recursive predicate).
Book ChapterDOI
Design Overview of the NAIL! System
TL;DR: The design decisions made for the NAIL! (not another implementation of logic!) system, an advanced form of DBMS where queries may involve a large collection of Prolog-like rules used for query interpretation, are described.
Proceedings ArticleDOI
On the equivalence of recursive and nonrecursive datalog programs
Surajit Chaudhuri,Moshe Y. Vardi +1 more
TL;DR: This work studies the problem of determining whether a given recursive Datalog program is equivalent to a given nonrecursion-based program and proves triply exponential upper and lower time bounds.
Journal ArticleDOI
Program derivation by fixed point computation
TL;DR: An abstract functional problem specification language SQ+, which is shown to express any partial recursive function in a fixed point normal form, and a nondeterministic iterative schema that in the case of finite iteration generalizes the “chaotic iteration” of Cousot and Cousot for computing fixed points of monotone functions efficiently.
References
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Proceedings ArticleDOI
Optimal implementation of conjunctive queries in relational data bases
TL;DR: It is shown that while answering conjunctive queries is NP complete (general queries are PSPACE complete), one can find an implementation that is within a constant of optimal.
Proceedings Article
Magic Sets and Other Strange Ways to Implement Logic Programs.
TL;DR: Several methods for implementing database queries expressed as logical rules, including a general algorithm for rewriting logical rules so that they may be implemented bottomUP (= forward chaining) in a way that cuts down on the irrelevant facts that are generated.
Proceedings ArticleDOI
Universality of data retrieval languages
Alfred V. Aho,Jeffrey D. Ullman +1 more
TL;DR: Although relational algebra and relational calculus satisfy these principles, there are certain queries involving least fixed points that cannot be expressed by these languages, yet that also satisfy the principles.
Proceedings ArticleDOI
Magic sets and other strange ways to implement logic programs (extended abstract)
TL;DR: Several methods for implementing database queries expressed as logical rules are given and they are compared for efficiency as mentioned in this paper, and one method, called "magic sets", is a general algorithm for rewriting logical rules so that they may be implemented bottom-UP in a way that cuts down on the irrelevant facts that are generated.
Journal ArticleDOI
Equivalences Among Relational Expressions with the Union and Difference Operators
TL;DR: It is shown that containment of tableaux is a necessary step in testing equivalence of queries with union and difference, and the containment problem is shown to be NP-complete even for tableaux that correspond to expressions with only one project and several join operators.