Introduction.  Business Process Execution Language for Web Services (called BPEL4WS or simply BPEL in the rest of this chapter) provides a means of specifying interactions between web services for accomplishing a potentially long running business task.

Used terms . 

  • WSDL .  Web Services Description Language as described in the corresponding W3C proposed recommendation. This is a notation for declaring services and the types of data they accept and produce. Also the term may be used to refer to the document containing a WSDL description.

  • partner .  A service or application which interacts with a BPEL process.

  • (BPEL) script .  A document containing BPEL compatible XML constructs.

  • (BPEL process) instance .  An instance of a BPEL process, can be running, suspended, aborted or finished.

  • activity .  An activity is a building block of a BPEL script. Receiving data, invoking other web services, programming language like control structures are all examples of activities.

  • portType .  Container for set of abstract operations see below.

  • operation .  An abstract black-box that have an XML input or/and output. Services potentially supports four types of operations: one-way, request-response, notification and solicit-response; this depends of input and/or output allowed and what is their order. The BPEL4WS uses one-way and request-response operations. Operations are grouped in 'ports' which define what operations a particular service supports.

  • message .  An abstract XML fragment that is used for operation input and output. In particular this is used inside SOAP Envelope and for value of the BPEL variables. Also the WSDL specification specifies how abstract messages will be used as concrete messages using the SOAP protocol and which encoding will be used.