The work presented here aims to provide a composition model of semantic web services. This model is based on a semantic representation of domain concepts handled by web services, namely, operations and the static concepts used to describe static properties of Web services. Different levels of abstraction are given to the concept of operation to allow gradual access to concret services. Thus, two different levels of the composition plan are generated (abstract and concret). This will reuse plans already constructed to meet similar needs even with modified preferences.