Idempotent single-predicate horn clauses

  • Peter T. Wood
  • Alberto O. Mendelzon
  • Paolo Atzeni
Logic And Deductive Databases
Part of the Lecture Notes in Computer Science book series (LNCS, volume 326)


Previous work has addressed the issues of idempotence and boundedness for various restricted classes of Horn-clause queries. In this paper, we consider queries consisting of a single clause containing a single predicate symbol. As such, these queries are a notational variant of the full, untagged tableau queries with recursive semantics. The study of the idempotence and boundedness for single-clause, single-predicate queries has previously been restricted to the typed case. We generalize these results to obtain syntactic, polynomial-time computable characterizations of idempotence for certain classes of untyped queries.


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Copyright information

© Springer-Verlag Berlin Heidelberg 1988

Authors and Affiliations

  • Peter T. Wood
    • 1
  • Alberto O. Mendelzon
    • 1
  • Paolo Atzeni
    • 2
  1. 1.Computer Systems Research InstituteUniversity of TorontoTorontoCanada
  2. 2.Dipartimento di Informatica e SistemisticaUniversita' di NapoliNapoliItaly

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