Conclusion

Web services expose interfaces of existing components using a standard web-based protocol. A client uses these interfaces to use the services provided by the components. A typical business process requires multiple web services. The involvement of web services from different developers required the creation of new standards to achieve proper coordination between them. Several new standards were developed to achieve this coordination. This chapter has discussed several such open standards that are required for the coordination of web services.

The WS-Security specification addresses how to transport security context between the participating processes and thus how to provide a secured distributed computing based on the collaboration of diverse web services. The WS-Coordination specification defines a framework that is used by participating processes to coordinate the desired activities between multiple processes.

Web Services Transactions require the coordination between multiple parties to implement a distributed transaction. They use the WS-Coordination specification for this purpose. As several messages are transported between diverse parties during a business process, reliable message delivery is required. The WS-Reliable Messaging specification addresses this issue. The messages are sent to endpoints. The WS-Addressing specification describes how to define such endpoints. Web services expose their interface with the help of service-description documents. The WS-Inspection specification helps in dynamic discovery of such documents. The WS-Policy specification describes the policies used by a process to its partners. Finally, the WS-Eventing specification helps in creating an event-based infrastructure for business collaborations.

When different web services are connected together to create a larger business process, there is a need to define the workflow to ensure the proper sequencing of these services. A new language, BPEL, is designed for this purpose. This chapter described briefly the need for this new language. Further chapters in the book will go into the depths of this language to understand how a business process is created in BPEL and describe the several tools that are available to develop BPEL documents.