Business Process Execution Language

Business Process Execution Language, usually shortened to BPEL and formally called WS-BPEL, is an XML-serialized language standardized by OASIS for describing how a business process coordinates web services. A process written in it exchanges information with the outside world only through web service interfaces, and it can be written either as an executable process that models the real behavior of one participant or as an abstract process that shows only the publicly visible message exchanges. The language grew out of two earlier efforts, the Web Services Flow Language from IBM and Xlang from Microsoft, which were merged into BPEL4WS and then renamed WS-BPEL 2.0 by the OASIS technical committee in 2004. It is an orchestration language rather than a choreography language, so one designer controls the sequence of messages. It offers structured constructs such as sequence, flow, if and while, scopes with fault and compensation handlers, and XPath 1.0 as its default expression language. It has no standard graphical notation, and extensions such as BPEL4People add human tasks to the model.