A requirements specification defines the requirements for the future system at a conceptual level (i.e., class or type level). In contrast, a scenario represents a concrete example of current or future system usage. In early RE phases, scenarios are used to support the definition of high level requirements (goals) to be achieved by the new system. In many cases, those goals can to a large degree be elicited by observing, documenting and analyzing scenarios about current system usage, i.e., the new system must often fulfill many of the functional and nonfunctional goals of the existing system. To support the elicitation and validation of the goals achieved by the existing system and to illustrate problems of the old system, we propose to capture current system usage using rich media (e.g., video, speech, pictures, etc.) and to interrelate those observations with the goal definitions. Thus, we particularly aim at making the abstraction process which leads to the definition of the conceptual models more transparent and traceable.
More precisely, we relate the parts of the observations which have caused the definition of a goal or against which a goal was validated with the corresponding goal. These interrelations provide the basis for: 1) explaining and illustrating a goal model to, e.g., untrained stakeholders and/or new team members, and thereby improving a common understanding of the goal model; 2) detecting, analyzing, and resolving a different interpretation of the observations; 3) comparing different observations using computed goal annotations; and 4) refining or detailing a goal model during later process phases. Using the PRIME implementation framework, we have implemented the PRIME-CREWS environment, which supports the interrelation of conceptual models and captured system usage observations. We report on our experiences with PRIME-CREWS gained in a first experimental case study.