Chapter Five. Business Process Execution Language (BPEL)

The Business Process Execution Language for Web Services (BPEL4WS, usually shortened to BPEL, which rhymes with "people") is, as its name suggests, a language for the definition and execution of business processes. Though it is not the only standard process language, BPEL is the most popular, and is beginning to saturate the process space.

There are two common ways to represent business processes: XML and notational. BPEL competes in the XML arena with BPML, XPDL, and other approaches. Notational languages include Business Process Modeling Notation (BPMN) and UML activity diagrams. Each type of representation has its merits and, as discussed in Chapter 2, a good BPM architecture requires both of them.

IBM, Microsoft, and BEA wrote the BPEL specification and subsequently handed it over to the WSBPEL technical committee of the OASIS organization (of which they are members) for standardization. The conceptual roots of BPEL coincide exactly with earlier BPM initiatives of each of the three companies: IBM's WSFL, Microsoft's XLANG and BEA's Process Definition for Java (PD4J) . As discussed in Chapter 3, WSFL is based on Petri nets and XLANG uses concepts of the pi-calculus; BPEL, consequently, is a mixture of these two theories. PD4J, as discussed later in this chapter, is the basis for the Java extension to BPEL, known as BPELJ.

This chapter explores several aspects of BPEL:

• Its authors and maintainers

• How to develop a BPEL process

• Java extensions to BPEL

• BPEL's support for common BPM patterns

• A substantial example of BPEL in action

NOTE

OASIS, or the Organization for the Advancement of Structured Information Standards (http://www.oasis-open.org), is a nonprofit consortium that develops, maintains, and promotes e-business standards, including ebXML, SGML, UDDI , PKI, and BPEL. Members include Adobe, AMD, BEA, BMC, Citrix, Computer Associates, Cyclone Commerce, Dell, Documentum, EDS, Entrust, Fujitsu, FundSERV, HP, Hitachi, IBM, IDS Scheer, Intel, IONA, Microsoft, NEC, Netegrity, Nokia, Novell, Oracle, PeopleSoft, Reuters, SAP, SeeBeyond, Sun, Tibco, Verisign, Vignette, Visa, webMethods, Wells Fargo, and Xerox. The BPEL 1.1 specification is published on the corporate web sites of each of its major authors.