Proceedings ArticleDOI
Safety of datalog queries over infinite databases
Yehoshua Sagiv,Moshe Y. Vardi +1 more
- pp 160-171
TLDR
It is proved that while weak safety is decidable, termination is not, and it is shown that a closely related problem, the decision problem for safety with respect to functional dependencies is undecidable even for monadic programs.Abstract:
A query is safe with respect to a set of constraints if for every database that satisfies the constraints the query is guaranteed to yield a finite set of answers. We study here the safety problem for Datalog programs with respect to finiteness constraints. We show that safety can be viewed as a combination of two properties: weak safety, which guarantees the finiteness of intermediate answers, and termination, which guarantees the finiteness of the evaluation. We prove that while weak safety is decidable, termination is not. We then consider monadic programs, i.e., programs in which all intensional predicates are monadic, and show that safety is decidable in polynomial time for monadic programs. While we do not settle the safety problem, we show that a closely related problem, the decision problem for safety with respect to functional dependencies, is undecidable even for monadic programs.read more
Citations
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Journal ArticleDOI
Constraint logic programming : A survey
Joxan Jaffar,Michael J. Maher +1 more
TL;DR: This survey of CLP is to give a systematic description of the major trends in terms of common fundamental concepts and the three main parts cover the theory, implementation issues, and programming for applications.
Journal ArticleDOI
Termination of logic programs: the never-ending story
Danny De Schreye,Stefaan Decorte +1 more
TL;DR: The structure of the termination proofs, the selection of well-founded orderings, norms and level mappings, the inference of interargument relations, and special treatments proposed for dealing with mutual recursion are outlined.
Elements of Relational Database Theory.
TL;DR: This paper is to provide a systematic and unifying introduction to relational database theory, including some of the recent developments in database logic programming.
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).
Journal ArticleDOI
Static analysis techniques for predicting the behavior of active database rules
TL;DR: Methods for statically analyzing sets of active database rules to determine if the rules are guaranteed to terminate, guaranteed to produce a unique final database state, and guaranteed toproduce a unique stream of observable actions are given.
References
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An amateur's introduction to recursive query processing strategies
TL;DR: In this article, the authors present a survey and comparison of various strategies for processing logic queries in relational databases, focusing on Horn Clauses with evaluable predicates but without function symbols.