An object-oriented and constraint-based knowledge representation system for design object modeling

FREEDOM (Framework for Representing and Elaborating Design Object Models), a system for design object modeling, is presented. An object model, represented as a set of objects in this system, is not a mere data structure but an active entity which works to solve design problems. The knowledge representation provided in the system, based on the object-oriented paradigm, makes it possible to describe constraints in declarative form. A class hierarchy is represented with links, and a class-instance relation can be changed dynamically. These features are useful for top-down refinement. The problem-solving mechanism of the system is based on constraint-satisfaction techniques. Constraints are declared statically and can be added to the objects dynamically. An object has a function, to keep its state satisfying given constraints. By this function, values of attributes and classes of objects that satisfy design requirements can be found. The constraint-satisfaction method is based on the technique of constraint logic programming and constraint propagation among objects. FREEDOM is implemented using the ESP language on a PSI machine