Chapter 3. The BPEL Engine

A BPEL engine executes BPEL business process instructions. The BPEL engine included as part of the JBoss Enterprise SOA Platform product is based on Apache ODE.

Business Process Execution Language (BPEL) is an OASIS-standard language for business rules orchestration. Refer to http://docs.oasis-open.org/wsbpel/2.0/wsbpel-v2.0.html for more information.

Business rule orchestration refers to the act of specifying actions within business processes via web services.

An enterprise service bus is a concrete implementation of an abstract SOA design philosophy. An enterprise service bus (ESB) has two roles: it provides message routing functionality and allows you to register services. The enterprise service bus that lies at the center of the JBoss Enterprise SOA Platform is called JBoss ESB.

An enterprise service bus deals with infrastructure logic, not business logic (which is left to higher levels). Data is passed through the enterprise service bus on its way between two or more systems. Message queuing may or may not be involved. The ESB can also pass the data to a transformation engine before passing it to its destination.

Apache ODE ("Orchestration Director Engine") is a software component that is designed to execute BPEL business processes. It sends and receives messages to and from web services, manipulates data and performs error handling in the method prescribed in your process definition. To learn more about Apache ODE, visit the project website at http://ode.apache.org/.

A BPEL Process Definition is an XML file that acts as a template for a process. when published, the process definition creates a process that is a web service in its own right.

A process instance is one execution of a process definition.