Total and partial well-founded Datalog coincide

  • Jörg Flum
  • Max Kubierschky
  • Bertram Ludäscher
Contributed Papers Session 2: Logic and Databases I
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1186)

Abstract

We show that the expressive power of well-founded Datalog does not decrease when restricted to total programs (it is known to decrease from Π11 to Δ11 on infinite Herbrand structures) thereby affirmatively answering an open question posed by Abiteboul, Hull, and Vianu [AHV95]. In particular, we show that for every well-founded Datalog program there exists an equivalent total program whose only recursive rule is of the form win(¯X) ← move(¯X,¯Y), ¬ win(¯Y) where move is definable by a quantifier-free first-order formula. This yields a nice new normal form for well-founded Datalog and implies that it is sufficient to consider draw-free games in order to evaluate arbitrary Datalog programs under the well-founded semantics.

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Copyright information

© Springer-Verlag 1997

Authors and Affiliations

  • Jörg Flum
    • 1
  • Max Kubierschky
    • 1
  • Bertram Ludäscher
    • 2
  1. 1.Mathematische FakultätUniversität FreiburgFreiburgGermany
  2. 2.Institut für InformatikUniversität FreiburgFreiburgGermany

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