Adding semantics to Web Services enable the automatic selection, mediation and composition of services across heterogeneous users and domains. The Semantic Web has the potential to provide the Web Services infrastructure with the information it needs through formal languages and ontologies for reasoning about service description, meaning of exchanged messages, etc. In this paper, we analyze several current approaches that implement Semantic Web Services by focusing on activities they are required to perform. These activities involve discovery, selection, mediation, and composition. We particularly analyze and compare how the approaches implement these activities by using semantics resources. We present a framework for comparison, which is used to highlight strengths and weaknesses as well as to detect topics for further research.