KADS is founded on modelling. Models in KADS are structured 3. Expertise Model. An abstract representation of the real world descriptions of observed or required behaviour. For example, problem solving processes. It records in a structured manner the human expert problem solving behaviour is represented in KADS expert problem solving requirements of the system. as a four layer model of expertise. At each level qualitatively 4. Global System Architecture. At the same level of abstraction as distinct aspects of the behaviour are addressed. Around this core the Process Model, the Global System Architecture represents idea a series of structural frameworks for representing a KBS at the structure and scope of the proposed system in terms of a set various points in development have been introduced. KBS develop- of subsystem and interface definitions. ment is thus viewed as consisting of a series of modelling tasks Q 5. Functional Design Model. This represents the structure and where the ultimate output of the development is an operational scope of the proposed system's problem solving component(s). model, i.e. an implemented system. It is a high level functional specification for the KBS. It is reached by a process of transforming the analysis models into Additionally, KADS supports the modelling of user/system inter- a set of functional elements. action based on an analysis of the tasks to be performed using the Behavioural Design Model. A representation of the design system. It also provides a document framework for recording more techniques (KBS or otherwise), algorithms and data structures general requirements and constraints. This ensures that any non which have been chosen to realise the elements of the Func- KBS specific areas which still impact on the development are covered. tional Design Model. 7. Physical Design Model. This represents the physical architec- KADS is primarily concerned with the the Analysis (Product ture of the target KBS in terms of a set of module definitions Definition) and Design (High Le