Paper:
Language: English:

Rough Set Approximation as Formal Concept

Nozomi Ytow^, David R. Morse^, and David McL. Roberts^

^Graduate School of Life and Environmental Sciences, University of Tsukuba
^Faculty of Mathematics and Computing, The Open University
^The Natural History Museum

Received: December 28, 2005

Accepted: April 1, 2006

Keywords: dual isomorphism, taxonomy, multiple hierarchy, concept comparison, concept analysis

Journal ref: Journal of Advanced Computational Intelligence and Intelligent Informatics, Vol.10, No.5 pp. 606-611, 2006

Abstract

Formal Concept Analysis (FCA) defines a formal concept as a pair of sets: objects and attributes, called extent and intent respectively. A rough set, on the other hand, approximates a concept using sets of objects only (in terms of FCA). We show that 1) a formal concept can be composed using a set of objects and its complement, 2) such object-based formal concepts are isomorphic to formal concepts based on objects and attributes, 3) upper and lower approximations of rough sets give generalization of formal concept, and 4) the pair of positive and negative sets (sensu rough set theory) are isomorphic to complemental formal concepts when the equivalence of the rough set gives positive and negative sets unique to each of the formal concepts. Implications of this are discussed.

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