BPEL(Business Process Execution Language)

BPEL is a process modeling/orchestration language that standardizes process descriptions in a markup language similar to XML, allowing for the integration of business process management and automated web service applications.

BPEL allows business process users to define what business process activities interact with web services defined using web service description standards (WSDL).BPEL enables the sending and receiving of data between process activities that can be fulfilled by services or applications. Business processes modeled in the industry-wide BPMN standard can be exported to BPEL for execution, allowing for the straight-through integration of business processes and web services.

References:

Business Process Execution Language (BPEL) Tutorial -
http://searchsoa.techtarget.com/generic/0,295582,sid26_gci1330911,00.html#

From UML to BPEL -
http://www.ibm.com/developerworks/webservices/library/ws-uml2bpel/

Exposing SOA Enabled C Apps as Web Services -
http://xml.sys-con.com/node/314105