This chapter provides an overview of the area of service composition. It does so byintroducing a generic architecture for service composition and using this architecture todiscuss some salient concepts and techniques. The architecture is also used as aframework for providing a critical view into a number of languages, standardizationefforts, and tools related to service composition emanating both from academia andindustry, and to classify them in terms of the concepts and techniques that theyincorporate or support (e.g. orchestration and dynamic service selection). Finally, thechapter discusses some trends in service-oriented software systems engineeringpertaining to service composition.