Making Hidden Semantics of Hierarchical Classifications Explicit

Concept hierarchies are semi-structured knowledge repositories used for organizing large amounts of documents. File systems, products taxonomies for the market place and the directories provided by Web portals are common examples of concept hierarchies. We take the perspective in which such knowledge sources are inherently distributed and we address the problem of allowing their interoperability. In this paper first we provide a formal semantics for concept hierarchies and then we use that formal framework to explore a number of linguistic issues crucial for interpreting the implicit knowledge represented there. Relevant phenomena addressed include word sense disambiguation WORDNET(r) has been used as sense repository), the explicitation of multiwords' semantics and the interpretation of coordinations. The Web directories of Google and Yahoo has been considered for a number of case studies