Web Services Reengineering: Finishing Touches - Summary

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In this chapter, we've explained how you can describe executable business processes using BPEL. BPEL processes are composed with Web services and exposed as Web services. Activities in the process referring to inbound or outbound Web services specify the abstract interface.

We discussed the relationship of BPEL to other XML languages such as WSDL, XML Schema, and XPath, and you learned how BPEL is used to implement stateful Web services. We examined the following BPEL concepts in detail:

• Basic activities and structured activities are the building blocks used to aggregate Web services and add business logic to them.

• PartnerLinks and partnerLinkTypes are used to describe the relationship between the business process and the external world.

• Properties and correlation sets provide the means to associate Web service messages with instances of business processes.

• Fault handlers and compensation handlers let you deal with exceptional situations and reverse the results of business logic that successfully completed before a problem was recognized.

• Event handlers define entry points into the process with business logic executed concurrently to the main process.

BPEL has helped SkatesTown reengineer its purchase order Web service with a business process. A major objective was achieved: the implementation of a Web service that is flexible with respect to changing business needs. The recursive Web service composition model enabled SkatesTown to incorporate both internal services and business-to-business interactions within the business process. The purchase order process is a stateful service that offers the additional capability to cancel running orders.

Like SkatesTown, a growing number of companies are exploiting Web services in similar ways. In the heterogeneous environment of B2B interactions, interoperability is an absolute must. The next chapter focuses on such aspects of Web services.

Resources

• Business Process Execution Language for Web Services (BPEL4WS)

  • http://dev2dev.bea.com/ technologies/webservices/BPEL4WS. jsp

  • http://www-106.ibm.com/developerworks/ webservices/library/ws-bpel/

  • http://msdn.microsoft.com/library/ default.asp?url=/library/en-us/dnbiz2k2/html/bpel1-1.asp

  • http://ifr.sap.com/bpel4ws/

  • http://www.siebel.com/bpel

• Web Service Definition Language (WSDL)

  • http://www.w3.org/TR/wsdl

  • http://www.w3.org/TR/wsdl20/

• Web Services Addressing (WS-Addressing)

  • http://msdn.microsoft.com/ws/2003/
    03/ws-addressing/

  • http://www-106.ibm.com/developerworks/ webservices/library/ws-add/

  • http://dev2dev.bea.com/technologies/ webservices/ws-addressing.jsp

• Web Services Flow Language (WSFL)

  • http://www-3.ibm.com/software/solutions/ webservices/ pdf/WSFL.pdf

• XLang

  • http://www.gotdotnet.com/team/xml wsspecs/XLANG-c/default.htm

• XML Schema

  • http://www.w3.org/TR/xmlschema-0

  • http://www.w3.org/TR/xmlschema-1

  • http://www.w3.org/TR/xmlschema-2

• XML Path Language (XPath)

  • http://www.w3.org/TR/xpath

  • http://www.w3.org/TR/xpath20/

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