Safety of datalog queries over infinite databases

Yehoshua Sagiv*, Moshe Y. Vardi

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

22 Scopus citations

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 finteness 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 intentional predicates, 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.

Original languageEnglish
Title of host publicationProc Eighth ACM SIGACT-SIGMOD-SIGART Symp Princ Database Syst
PublisherPubl by ACM
Pages160-171
Number of pages12
ISBN (Print)0897913086, 9780897913089
DOIs
StatePublished - 1989
EventProceedings of the Eight ACM SIGACT-SIGMOD-SIGART Symposium on Principles of Database Systems - Philadelphia, PA, USA
Duration: 29 Mar 198931 Mar 1989

Publication series

NameProc Eighth ACM SIGACT-SIGMOD-SIGART Symp Princ Database Syst

Conference

ConferenceProceedings of the Eight ACM SIGACT-SIGMOD-SIGART Symposium on Principles of Database Systems
CityPhiladelphia, PA, USA
Period29/03/8931/03/89

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