Declarative objects for simulation

The general aim of the work is to allow a non-expert programmer to develop simulations, in particular for training purposes. For example, simulations of machinery to support fault-finding exercises can be constructed readily with the system described. It is expected that the simulation builder will be primarily interesting in the production of computer-based training material, but would be supported by a domain specialist, familiar with the machine being simulated. Other requirements include the provision of an interactive user interface both for development and debugging, a well a a clean interface to special user interfaces for training purposes. It is, also expected that a partially complete simulation can be tested without problems. With these requirements in mind, an object-oriented programming model was developed, together with supporting tools. This system was evaluated by constructing several simulations; one of these is described briefly. An unusual feature, however, is that the objects have declarative properties, based on a notion of attributes whose values are functions of other attributes. The same language and system was used both for building simulations and for user interface construction, although in this paper only the simulation aspects considered. As part of the evaluation of the modelling system, a simulation of a hydraulically-operated steel press was created