You can generate Business Process Execution Language for Web Services (BPEL4WS, or BPEL for short) from a BPMN Business Process diagram. BPEL is an XML-based language for describing a business process in which all the tasks are implemented by web services. It is intended to be a description that can be executed by a BPEL engine.
BPMN provides a notation that is readily understandable by all business users, from the business analysts that create the initial drafts of the processes, to the technical developers responsible for implementing the technology that perform those processes, and finally, to the business people who manage and monitor those processes. Therefore, BPMN has created a standardized bridge for the gap between the business process design and process implementation. BPMN has also been designed to visualize the execution of business processes using languages such as BPEL.
BPMN is a Business Process Modeling notation whereas BPEL is an execution language. Although there is high degree of correspondence between the two, there is not a perfect one-to-one mapping between them and a business process might not always meaningfully map to some thing that is executable. BPMN describes combinations of processes that can be executed manually and automatically.