The authors propose a methodology for business process choreography. This methodology provides specifications of two types of business processes (contract processes and executable processes) and an interface protocol to represent interoperability patterns between the processes. With their approach, existing processes usually managed by companies? own internal workflow management systems can be put together for collaboration and interact with each other through a common business process. They also implemented a prototype business process management system to support their business process choreography methodology. The system facilitates creation and instantiation of contract processes and manages an automatic execution of the Interface Protocol.