More on tractable disjunctive Datalog

Sometimes it is more natural to express knowledge in disjunctive Datalog rather than in ordinary Datalog. Several highly complex variants of disjunctive Datalog have been proposed in the past and their expressive power has been studied. In this paper we investigate tractable fragments of disjunctive...

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Bibliographic Details
Published in:	The journal of logic programming Vol. 46; no. 1; pp. 61 - 101
Main Authors:	Ben-Eliyahu-Zohary, Rachel, Palopoli, Luigi, Zemlyanker, Victoria
Format:	Journal Article
Language:	English
Published:	Elsevier Inc 01.11.2000
Subjects:	Disjunctive logic programming Expressive power of query languages Head-cycle-free programs Non-deterministic semantics Polynomial-time queries Head-cycle-free programs Disjunctive logic programming Polynomial-time queries Expressive power of query languages Non-deterministic semantics
ISSN:	0743-1066, 1873-5789
Online Access:	Get full text
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Summary:	Sometimes it is more natural to express knowledge in disjunctive Datalog rather than in ordinary Datalog. Several highly complex variants of disjunctive Datalog have been proposed in the past and their expressive power has been studied. In this paper we investigate tractable fragments of disjunctive Datalog. Algorithms are presented to answer queries defined using these fragments and their complexity analyzed. Furthermore, the expressive power of these tractable subsets is studied. The most expressive of the languages considered here is shown to express, in some sense explained in the paper, all polynomial time queries. This is the first identified fragment of disjunctive Datalog with this property.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23
ISSN:	0743-1066 1873-5789
DOI:	10.1016/S0743-1066(99)00066-7