Chapter Thirteen. BPEL4WS and Application Integration

We are clearly moving toward standards within the world of application integration, both at the information (e.g., XML) and services (e.g., Web services) layers. However, the notion of standards-based process integration, despite a few attempts such as WFMC (discussed in previous books), has not been as well accepted.

With the appearance of Business Process Execution Language for Web Services (BPEL4WS), a derivative of Web services, we have yet another attempt to provide a standard mechanism to define, execute, and share processes. BPEL4WS seems to have more momentum than earlier specifications, with adoptions by most major application integration technology vendors as well as enterprise software vendors. Moreover, its use of Web services and XML-like syntax makes it a natural fit for most consumers of technology. The goal is to provide a standard mechanism to define business processes that span application vendors, platforms, process engines, and application integration technology.

What's important here is that you understand the basics of the specification, what it is, and what it brings to process integration as we defined it earlier in the book, as well as its extension to B2B problem domains. The BPEL4WS specification is the primary reference material for this chapter, and once again we are going to cover the basics and the relation of this technology to application integration. Thus, you may go directly to the spec for more detail, certainly for more code, but the highlights are covered here.

There are a couple of aspects to process integration standards, including common formats for processes, metadata, and information, and a common set of notations that can span many products. Until now, the use of standards has been widely published but rarely employed. Indeed, most process integration layers either bound to an application integration technology or not are proprietary in nature.

The movement of Web services has launched a variety of substandards, or standards that use the notion and enabling technology of Web services in order to define them. BPEL4WS has such a standard. BPEL4WS is focused on the creation of complex processes by joining together local and remote services, thus leveraging the notion of process integration as well as service-oriented Web services.

In the world of BPEL4WS, process is one of two things:

• Executable business processes that model actual behavior of a participant in business interaction

• Business protocols that use process descriptions specifying the mutually visible message exchange's behavior for each of the parties leveraging the protocol (does not reveal internal behavior)

Process descriptions for business protocols are known as abstract processes, and BPEL4WS models behavior for both abstract and executable processes.

To this end, BPEL4WS leverages a well-defined language to define and execute business processes and business interaction protocols, thus extending the Web services interaction model by providing a mechanism to create meta applications process models, really above the existing services that exist inside or outside the company.^[1]

^[1] Business Process Execution Language for Web Services, Version 1.0. July 31, 2002.

What's both different and compelling about BPEL4WS is the use of a common syntax that is designed to be transferable from process engine to process engine. This is in contrast to other process integration standards, such as BPMI or WFMC, which are more about approaches than a common language. There is more momentum beyond BPEL4WS, and all technology vendors are declaring support for BPEL4WS.