A constraint-based UIMS using graph unification

Abstract

This paper describes an experimental UIMS developed to investigate methods of combining and reusing objects within a constraint-based system. A novel approach based on graph-unification facilitated the definition of composite objects and allowed behaviours to be transferred easily from one object to another. A very simple form of local propagation was used as the constraint satisfaction mechanism, which, as well as being fast, could also cope with cyclic dependencies. This method used a time-stamping method which made it possible to express time-dependency in the constraints. The system has features from both class-based and prototype-based object-oriented languages. Dynamic modification of objects can be performed rapidly enough for interactive control. Interfaces built with the system include a variety of 'standard' user interface objects such as sliders as well as a number of physical simulations utilising time-dependent constraints.