’’Corner‘‘ Relations in Allen‘s algebra

  • Authors:

  • Gérard Ligozat

  • Affiliations:

  • LIMSI/CNRS and Université Paris-Sud, Bldg. 508, 91403 Orsay, France

  • Venue:
  • Constraints
  • Year:
  • 1998

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Abstract

This paper proves a key result in the maximality proofof ORD-Horn relations, namely, the fact that any subclass ofAllen‘s algebra which contains all atomic relations, is closedunder conversion, intersection and composition, and containsa relation which is not ORD-Horn will contain one (in fact, twoat least) of four specific relations, the ’’corner‘‘ relations. Our proof uses the structural properties of ORD-Horn relations,where the original proof was by machine enumeration.