Service oriented modeling is gaining acceptance among academia and industry as a computing paradigm for business and systems integration. Its strong decoupling between service provision and consumption enables much more flexible and cost-effective integration, within and across organizational boundaries, than existing middleware or workflow systems do. However, it also creates new requirements for handling effective service discovery, dynamic service interoperation and automation support for service composition. Web services have been emerging as the lead implementation of SOA upon the Web. The related technologies define common standards that ensure interoperability between heterogeneous platforms. Nevertheless, they fail in satisfying SOA requirements. Semantic Web services initiatives have then emerged with the objective of providing the foundation to overcome these requirements. The main idea is extending service description with machine interpretable information that software programs can reason over it. This chapter discusses how far Web services and semantic Web services initiatives satisfy SOA requirements.