XLANG is a notation for the automation of business processes based on Web Services for the specification of message exchange behavior among participating Web Services. XLANG is expected to serve as the basis for automated protocol engines that can track the state of process instances and help enforce protocol correctness in message flows.
Devs Should Brace for Wave of Process, Modeling Tools Integration Developers, CA - Apr 11, 2008 ... WS-ReliableMessaging, WS-Addressing, Extensible Process Definition Language (XPDL), Microsoft's XLANG and the W3C working group on Choreography.