Issues raised in development of a large knowledge-based system for the design of railway signalling schemes

This paper looks at some of the issues raised during the early stages of development of a system to aid railway signalling engineers in their design work. It points to the paramount importance of the interface in the overall system design and how it may even affect the underlying system structure. The difficulties that can be encountered where a user interface cannot be specified are highlighted. The paper also considers the necessity for an intermediate representation of large, complex problem domains and emphasizes the need to consider future developers as users of the system. The focus of the three-year research project was the application of knowledge-based (or `expert´) systems (KBSs) to the design of modern railway signalling schemes with British Rail Solid State Interlocking (SSI) equipment. The KBS was christened CADDIE (computer aided data design integrated environment). It was developed using KEE and contained three main components: the track plan model; the SSI database and the route related objects. The design philosophy, the knowledge acquisition process and user interface design are discussed