In spite of many standards efforts, Web services with similar or compatible functionalities often have heterogeneous semantics. One reason is the disparate ontologies used for service descriptions. In order to compare and compose Web services, the ability to merge different ontologies is essential. This paper describes an approach to align numerous, independently designed ontologies. Our approach is a completely automated one, without the need for prior agreement on semantics. It incorporates WordNet and heuristic reasoning and infers new knowledge by selflearning. Our system provides a solid base for the seamless integration of Web services.