The BPEL Service Engine

The BPEL Service Engine provides runtime services for deploying BPEL processes. The BPEL Service Engine is used to execute WS-BPEL 2.0 (or simply BPEL) compliant business processes. WS-BPEL 2.0 (Web Services Business Process Execution Language) is an XML-based language used to program business processes.

Business processes typically involve the exchange, or orchestration, of messages between the process and other web services known as partner services. The contract between a business process and partner services is described in WSDL 1.1. The message exchange between a business process and partner services is wrapped in the WSDL 1.1 message wrapper, as defined by the JBI specification, and routed via the JBI Normalized Message Router (NMR). The NMR interacts with external web services, not resident on the local JVM, via binding components. Binding components are responsible for encapsulating protocol-specific details. Transactions between the BPEL Service Engine and collocated EJBs or web components are handled through the Java EE service engine.

WS-BPEL 2.0 utilizes several XML specifications: WSDL 1.1, XML Schema 1.0, XPath 1.0, and XSLT 1.0. Note that the JBI specification is targeted toward WSDL 2.0 and accommodates WSDL 1.1 by defining the wrapper. The BPEL Service Engine supports one-way, request-response operations (as defined in WSDL 1.1), within stateful, long-running interactions that involve two or more parties. Asynchronous request-response is accomplished using two one-way operations, one implemented by a partner, the other implemented by the business process using correlation.