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BPEL: Service composition for SOA

Get started developing business processes based on the Business Process Execution Language

By Matjaz B. Juric, JavaWorld.com, 07/10/06

BPEL (Business Process Execution Language) has become one of the most important technologies of SOA (service-oriented architecture) and enables easy and flexible composition of services into business processes. BPEL is particularly important because it introduces a new concept into application development—programming-in-the-large. This concept enables us to develop processes quickly by defining the order in which services will be invoked. This way, applications (and information systems) become more flexible and can better adapt to the changes in business processes.

Business processes are usually of dynamic nature. Companies have to improve and modify, act in an agile manner, optimize, and adapt processes to improve the responsiveness of the whole company. Every change and improvement in a business process has to reflect in applications that provide support for them. Although this requirement may not sound very difficult to fulfill, the real-world situation shows us a different picture. Changing and modifying applications is often a difficult job, which requires time. Therefore applications cannot react instantly to changes in business processes—rather, they require some time to implement, test, and deploy the modifications.

Making information systems more flexible and adaptable to changes, and better aligned with business processes is the major promise of SOA. In this article, I show why BPEL is so important and demonstrate how to develop a BPEL process.

Service-oriented approach

The SOA approach for efficient automation of business processes requires:

  • Standardized way to expose and access the functionality of applications as services
  • Enterprise bus infrastructure for communication and management of services, including message interception, routing, transformation, etc.
  • Specialized language for composition of exposed functionalities of applications into business processes

The first requirement is fulfilled by the latest distributed architecture—Web services. The second requirement is fulfilled by the ESB (enterprise service bus), which provides support for centralized, declarative, and well-coordinated management of services and their communications. The third requirement, composition of services into processes, is fulfilled by BPEL, the commonly accepted specialized language for business process definition and execution.

A business process, as seen by BPEL, is a collection of coordinated service invocations and related activities that produce a result, either within a single organization or across several. For example, a business process for planning business travels will invoke several services. In an oversimplified scenario, the business process will require us to specify the employee name, destination, dates, and other travel details. Then the process will invoke a Web service to check the employee status. Based on the employee status, it will select the appropriate travel class. Then it will invoke Web services of several airline companies (such as American Airlines, Delta Airlines, etc.) to check the airfare price and buy the one with the lowest price.

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