Abstract
Matching concepts against patterns (concepts with variables) is a relatively new operation that has been introduced in the context of concept description languages (description logics). The original goal was to help filter out unimportant aspects of complicated concepts appearing in large industrial knowledge bases. We propose a new approach to performing matching, based on a 'concept-centred' normal form, rather than the more standard 'structural subsumption' normal form for concepts. As a result, matching can be performed (in polynomial time) using arbitrary concept patterns of the description language ALN, thus removing restrictions from previous work. The paper also addresses the question of matching problems with additional 'side conditions', which were motivated by practical needs. Key words: Knowledge representation, description logics, matching.