On critical sets of a finite Moore family

Abstract

Cluster collections obtained within the framework of most cluster structures studied in data analysis and classification are essentially Moore families. In this paper, we propose a simple intuitive necessary and sufficient condition for some subset of objects to be a critical set of a finite Moore family. This condition is based on a new characterization of quasi-closed sets. Moreover, we provide a necessary condition for a subset containing more than k objects (k ≥ 2) to be a critical set of a k-weakly hierarchical Moore family. Finally, as a consequence of this result, we identify critical sets of some k-weakly hierarchical Moore families and thereby generalize a result earlier obtained by Domenach and Leclerc in the particular case of weak hierarchies.