Book Image

Business Process Execution Language for Web Services

Book Image

Business Process Execution Language for Web Services

Overview of this book

Web services provide the basic technical platform required for application interoperability. They do not, however, provide higher level control, such as which web services need to be invoked, which operations should be called and in what sequence. Nor do they provide ways to describe the semantics of interfaces, the workflows, or e-business processes. BPEL is the missing link to assemble and integrate web services into a real business process BPEL4WS standardizes process automation between web services. This applies both within the enterprise, where BPEL4WS is used to integrate previously isolated systems, and between enterprises, where BPEL4WS enables easier and more effective integration with business partners. In providing a standard descriptive structure BPEL4WS enables enterprises to define their business processes during the design phase. Wider business benefits can flow from this through business process optimization, reengineering, and the selection of most appropriate processes . Supported by major vendorsó including BEA, Hewlett-Packard, IBM, Microsoft, Novell, Oracle, SAP, Sun, and othersó BPEL4WS is becoming the accepted standard for business process management. This book provides detailed coverage of BPEL4WS, its syntax, and where, and how, it is used. It begins with an overview of web services, showing both the foundation of, and need for, BPEL. The web services orchestration stack is explained, including standards such as WS-Security, WS-Coordination, WS-Transaction, WS-Addressing, and others. The BPEL language itself is explained in detail, with Code snippets and complete examples illustrating both its syntax and typical construction. Having covered BPEL itself, the book then goes on to show BPEL is used in context. by providing an overview of major BPEL4WS servers. It covers the Oracle BPEL Process Manager and Microsoft BizTalk Server 2004 in detail, and shows how to write BPEL4WS solutions using these servers.
Table of Contents (14 chapters)
Business Process Execution Language for Web Services
Credits
About the Authors
About the Reviewers
Preface
Index

Chapter 4. Advanced BPEL

In the previous chapter, we covered the basics of BPEL and provided an introduction to the structure of business processes. We are now familiar with defining business processes, invoking web service operations sequentially and in parallel, defining partner links, defining variables, and assigning values. However, using BPEL for complex real-world business processes requires additional functionality. Sometimes the activities of a business process need to be performed in loops. Often activities might have links that would affect the execution order. This is usually the case with concurrent flows. Sometimes we will have to wait either for a message event or an alarm event to occur.

One very important aspect of business process modeling is fault handling. Particularly in business processes that span multiple enterprises and use web services over the Internet, we can assume that faults will occur quite often due to various reasons, including broken connections, unreachable...