partners are abstracted as Web services, we have introduced additional constructs to represent human users and define human interaction patterns. Each business process defined in our xBPEL extension has an external interface defined in the Web Service Definition Language (WSDL) that applications use to initiate the process. At invocation time, the business process accepts configuration parameters such as actual human participants and acceptable communication devices. Because all communication messages exchanged in PerCollab are defined in WSDL, the system components are interoperable with other Web services. Engine and translator The driving component in PerCollab is the BPEL engine, which determines the list of required business tasks and the order in which the system performs these tasks based on the process definition. The engine executes human tasks by dispatching them to the corresponding participants via the interaction controller. In addition to human users, Web services can act...