From Stakeholder Needs to Service Requirements

Web services offer a novel open, distributed computing environment. Within that environment, web services need to be discovered and composed in order to meet user needs (or, goals). For example, a user goal may be "plan a holiday". To fulfill this goal, several services need to be discovered from different directories, such as "book hotel", "book flight", "rent car" and "pay by credit card". These then need to be composed into a plan ("process). In this work, we adopt and extend an agent-oriented software design methodology (Tropos) and tailor it to the design of web services. We also sketch how Tropos design-time models can support service discovery and composition by offering a roadmap that relates stakeholder goals to collections of services available in different directories. A case study from the literature is used throughout.