Communication services are evolving at an unprecedented rate. No longer limited to interpersonal vocal communication, they now integrate functions such as address books, content sharing and messaging. The emergence of social networks – which may also include these features – is an important element of this transformation. Content services are becoming flagship services themselves, and are sometimes paired up with conversation services. The boundaries between different services are becoming less and less distinct. This book meets the need for a better understanding of communication services, and for a general framework of their description. A detailed overview on service architecture in the Telco, Web and IT worlds is presented, offering a roadmap with explanations on how to improve the architecture and governance of communication service architectures by exploiting the syntax and semantics that are common to different services is clearly outlined. This book also responds to recurring questions about service design, such as the functional scope of enablers or SOA (Service Oriented Architecture) services, the relevance of service composition to the user and collaboration between different services in a converged environment. Many concrete examples from telecoms service providers’ operations illustrate these concepts.