The use of communities provides a scalable solution for gathering and managing functionally-equivalent Web services. In order to ensure single access to the community, a community uses a common interface that acts as a proxy and selects other Web services in the community. However, Web services adopt different semantics for representing the data they receive and send. These semantics must be adapted to conforming to the community semantics. In this paper, we present a solution to this problem. Our solution is based on the use of context in order to explicitly describe semantic discrepancies within a community. We rely on a semantic annotation of WSDL descriptions to describe the semantics attached to Web services, and we provide mediation mechanisms at the community level to handle semantic heterogeneities between Web services and the community. We validate our solution through implementation and experimentation over a test community and show the limitations of our approach. Copyright 2008 ACM.