Web services composition is an emerging paradigm for application integration within and across organizational boundaries. A landscape of languages and techniques for web services composition has emerged and is continuously being enriched with new proposals from different vendors and coalitions. However, little effort has been dedicated to systematically evaluate the capabilities and limitations of these languages and techniques. The work reported in this paper is a step in this direction. It presents an in-depth analysis of the Business Process Execution Language for Web Services (BPEL4WS) with respect to a framework composed of workflow and communication patterns. Keywords: web services composition, business process modeling, interorganizational workflow, BPEL4WS.