3 Bioern Bioernstad Cesare Pautasso Gustavo Alonso 2006 2006 IEEE International Conference on Services Computing Chicago, USA Although workflow languages are widely used for composing discrete services, these are not suitable for stream based interactions. In this paper we address the problem of how to extend a conventional Web service composition language with the ability to deal with data streaming services. The paper discusses several modeling alternatives and presents a marker based semantics for safely dealing with pipelined processing in service compositions. The paper also presents application examples that illustrate the advantages of the proposed approach