Expressibility of bounded-arity fixed-point query hierarchies

  • Authors:

  • P. Dublish;S. N. Maheshwari

  • Affiliations:

  • Dept. of Computer Science & Engg., I.I.T. Kanpur, Kanpur, India - 208016;Dept. of Computer Science & Engg., I.I.T. Delhi, New Delhi, India - 110016

  • Venue:
  • PODS '89 Proceedings of the eighth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
  • Year:
  • 1989

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Abstract

The expressibility of bounded-arity query hierarchies resulting from the extension of first-order logic by the least fixed-point, inductive fixed-point and generalized fixed-point operators is studied. In each case, it is shown that increasing the arity of the predicate variable from k to k+1 always allows some more k-ary predicates to be expressed. Further, k-ary inductive fixed-points are shown to be more expressive than k-ary least fixed-points and k-ary generalized fixed-points are shown to be more expressive than k-ary inductive fixed-points.