Web service technology has grown rapidly in recent years and continues to attract strong attention from both researchers and industry. Yet, a single service on its own is rarely enough to satisfy the complex demands placed by today's users. This has made service integration an important direction, since organizations increasingly need to connect different applications and resources across partners to deliver a complete solution. At present, however, many of the available systems still fall short of user expectations because they struggle to combine services in a smooth and reliable way. Coordinating the logic of different services, whether at the functional level or within broader business processes, remains a major challenge. In this chapter, I set out a brief introduction to web services, their key components, and the reasons why coordination is necessary. The discussion also touches on the role of business policies, and it closes by outlining the research issues, objectives, and contributions that shape the study.