Modelling Interaction Properties for Interactive Case Memories

Previous work on formal models for interactive systems has often used text editors and graphics editors as case studies. Consequently the notations developed do not necessarily include all the facilities that may be required in reasoning about other types of interactive system. In this chapter two possible interaction requirements for an interactive knowledge based system (IKBS), user-initiated recoverability and user-initiated reachability are considered. A two-level model based on the work of Sufrin and He [18] is used to show how these requirements can be expressed formally using the Z notation. This model is unable to support the structuring of specifications from collections of interacting components. Three specification notations, which can support structured specification, are then compared in terms of their powers to express these interaction requirements. We show that none of the specially designed notations is capable of adequately expressing the interaction requirements of userinitiated reachability and user-initiated recoverability in ICMs, although all the notations have been successfully applied to the specification of other types of system.