Improper specification of systems requirements has thwarted many splendid efforts to deliver high-quality information systems. Scholars have linked this problem to, between others, poor communication among systems developers and users at this stage of systems development. Some believe that specifying requirements is the most important and the most difficult activity in systems development. However, limitations in human information processing capabilities and the inadequacy of the structures available for communicating specifications and obtaining feedback and validation help to exacerbate the difficulty. This chapter presents an overview of both longstanding and newer requirements specification models and evaluates their capability to advance user participation in this process and incorporate stated quality attributes. It also reports on preliminary evaluations of animated system engineering (ASE), the author's preferred (newer) technique, which indicate that it has the capability to improve the specification effectiveness.