Business Process Execution Language

The Web Services Business Process Execution Language (WS-BPEL), commonly known as BPEL (Business Process Execution Language), is an OASIS standard executable language for specifying actions within business processes with web services. Processes in BPEL export and import information by using web service interfaces exclusively.

One can describe Web-service interactions in two ways: as executable business processes and as abstract business processes.

WS-BPEL aims to model the behavior of processes, via a language for the specification of both Executable and Abstract Business Processes. By doing so, it extends the Web Services interaction model and enables it to support business transactions. It also defines an interoperable integration model that should facilitate the expansion of automated process integration both within and between businesses. Its development came out of the notion that programming in the large and programming in the small required different types of languages.

As such, it is serialized in XML and aims to enable programming in the large.

The concepts of programming in the large and programming in the small distinguish between two aspects of writing the type of long-running asynchronous processes that one typically sees in business processes:

The origins of WS-BPEL go back to Web Services Flow Language (WSFL) and Xlang.

In 2001, IBM and Microsoft had each defined their own fairly similar, "programming in the large" languages: WSFL (Web Services Flow Language) and Xlang, respectively. Microsoft even went ahead and created a scripting variant called XLANG/s which would later serve as the basis for their Orchestrations services inside their BizTalk Server. They specifically called it a "proprietary (language) and (that) is not fully documented."

With the advent and popularity of BPML, and the growing success of BPMI.org and the open BPMS movement led by JBoss and Intalio Inc., IBM and Microsoft decided to combine these languages into a new language, BPEL4WS. In April 2003, BEA Systems, IBM, Microsoft, SAP, and Siebel Systems submitted BPEL4WS 1.1 to OASIS for standardization via the Web Services BPEL Technical Committee. Although BPEL4WS appeared as both a 1.0 and 1.1 version, the OASIS WS-BPEL technical committee voted on 14 September 2004 to name their spec "WS-BPEL 2.0". (This change in name aligned BPEL with other Web Service standard naming conventions which start with "WS-" (similar to WS-Security) and took account of the significant enhancements made between BPEL4WS 1.1 and WS-BPEL 2.0.) If not discussing a specific version, the moniker BPEL is commonly used.

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