Abstract
Web services allow developers to create, generate and compose them at runtime. However, a single web service is not sufficient to achieve most of user demands in its own. This gives rise to the concept of web services composition of is an appropriate solution to maximize the benefits of web services. Web services composition has received a great attention from different communities. A number of different semantic standards/specifications have been proposed to tackle this issue. These standards are Ontology Web Language and Web Service Modeling Ontology. In this paper, we provide an overview of these standards and present a comparison between them. We also overview different applications that have developed based on each of these standards and present comparisons among them.