On the evolution of services

In an environment of constant change and variation driven by competition and innovation, a software service can rarely remain stable. Being able to manage and control the evolution of services is therefore an important goal for the Service-Oriented paradigm. This work extends existing and widely adopted theories from software engineering, programming languages, service-oriented computing, and other related fields to provide the fundamental ingredients required to guarantee that spurious results and inconsistencies that may occur due to uncontrolled service changes are avoided. The paper provides a unifying theoretical framework for controlling the evolution of services that deals with structural, behavioral, and QoS level-induced service changes in a type-safe manner, ensuring correct versioning transitions so that previous clients can use a versioned service in a consistent manner.