Whereas building and enriching ontologies are complex and tedious tasks, only few tools propose a complete solution to assist users. This paper presents POEM (Platform for Ontology crEation and Management) which provides a complete environment for ontology building, merge and evolution. POEM’s algorithms are based on existence constraints and Boolean equations that allow to capture the semantic of concepts. POEM also integrates a semantic fusion that relies on WordNet and supports different storage formats. The different functionalities are implemented as a set of web services.