Abstract
Web service processes are business processes composed of individual Web services. Web service process description languages, used in both choreography and orchestration, are influenced by techniques from workflow modeling, formal methods and software engineering. Since such languages are based on software scripts to be executed by a process engine, their expressive power indeed is beyond classic discrete event system models, such as process algebra and Petri nets. This chapter analyzes and compares different Web service process description languages, discusses the issues in using discrete event system models to model Web service processes, and also compares Web service processes with workflow processes. The chapter also discusses the suitable methods based on the formal models for various computing tasks, such as verification and validation.