In this study, the original subsumption rule proposed by Sanderson and Croft is revised. Different thresholds are used to observe how shapes of a concept hierarchy change. Ranking among children concepts is available based on sorted subsumption data. This study also explores three potential usages of concept hierarchies. 1. As an overview to a document collection 2. As a tool to compare different document collections in the same domain 3. As a tool to observe evolution trends in a domai
