The Role of Metadata in the Orchestration of Web Services

“Orchestration is the study and practice of arranging music for an orchestra or musical ensemble. In practical terms it consists of deciding which instruments should play which notes in a piece of music.” [Wiki] In musical terms, the orchestra would be made up of Web services, BPEL would be the sheet music and the business process manager (BPM) would be the composer that selects the necessary Web services and decides how they should interact with each other.

Organizations use Web services in two broad categories, Enterprise Application Integration (EAI) and Business-to-Business (B2B) e-commerce as well as less complex scenarios such as technical functions and information services (common services1). This thesis provides an insight on how the Web service standards resolve the limitations of conventional middleware and extend the benefits of process management to a wider scope of business problems.

Web service standards like SOAP, XML, WSDL, and BPEL enable customers to solve integration problems easily by providing interoperability within a company or across multiple companies and improve B2B eCommerce and supply chain management by shifting to a service-oriented paradigm in application development. Web service orchestration provides an open, standards-base approach to create high-level business processes, such as workflows.

This thesis will focus on BPEL for describing the business logic, although competing standards are still in use. The steps for the workflow implementation will be explained on the basis of a sample procurement scenario.

The second chapter “Process Management and Web Services” gives an insight into Enterprise Application Integration (EAI) and Workflow Management Systems (WfMS) and how Web services resolve the limitations of these middleware technologies.

Web service technologies are based on the use of several XML dialects to exchange data between applications. Chapter 3 “Introduction to XML-Technologies” describes the basics of the markup language and its technologies. Because XML is a huge topic the focus of this chapter lies primarily on what is needed to understand Web services technologies.