The lattices of closure systems, closure operators, and implicational systems on a finite set: a survey

  • Authors:
  • Nathalie Caspard;Bernard Monjardet

  • Affiliations:
  • LACL, Université Paris 12, 61 avenue du Général de Gaulle, 94010 Créteil Cedex, France;CERMSEM, Maison des Sciences Économiques, Université Paris 106-112 boulevard de l'Hôpital 75013 Paris, France

  • Venue:
  • Discrete Applied Mathematics - Special issue: The 1998 conference on ordinal and symbolic data analysis (OSDA '98)
  • Year:
  • 2003

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Abstract

Closure systems (i.e. families of subsets of a set S containing S and closed by set intersection) or, equivalently, closure operators and full implicational systems appear in many fields in pure or applied mathematics and computer science. We present a survey of properties of the lattice of closure systems on a finite set S with proofs of the more significant results. In particular we show that this lattice is atomistic and lower bounded and that there exists a canonical basis for the representation of any closure system by "implicational" closure systems. Since the lattices of closure operators and of full implicational systems are anti-isomorphic with the lattice of closure systems they have the dual properties.