Book excerpt: Services and service oriented computing have emerged and matured over the last decade, bringing with them a number of available services that are selected by users and developers and composed into larger applications. The Handbook of Research on Non-Functional Properties for Service-Oriented Systems: Future Directions unites different approaches and methods used to describe, map, and use non-functional properties and service level agreements. This handbook, which will be useful for both industry and academia, provides an overview of existing research and also sets clear directions for future work.