Abstract: Concurrent Transaction Logic (CI}R) is an extension of predicate logic which supports reasoning the automatic composition of semantic Web Services. This paper used CTR as the describing and reasoning tools, and proposed a composition method from the two aspects of OWI: S Web Services:function and behavior. The executing semantics of CTR and the procedural semantics of its Horn clause reduce the reasoning complexity. A polynomial time algorithm was constructed. This paper provided a new method for handling the problem that current mainstream semantic Web service composition methods arc not able to model concurrent behaviors.

Key words: Semantic Web service, Service composition, Concurrent transaction logic, Horn clause