Building models for reasoning in qualitative physics

A method of automatically constructing a model or a set of constraints from domain principles to solve the dynamic behavior of a mechanical system through qualitative simulation is presented. Two issues are emphasized: (1) the extraction of a necessary and sufficient set of system constraints that provides the minimum uncertainty associated with qualitative simulation, from the fundamental principles and laws of physics and based solely on the physical description of a given mechanical system; and (2) the modification of system constraints through time by detecting and identifying system discontinuities due to collisions, separations, and other critical states associated with each system object. The first is accomplished by describing a mechanical system by a collection of object and interconnection primitives which allows direct invocations and instantiations of all the relevant physics laws from the knowledge base. The second is accomplished by monitoring whether the states of any individual subsystems evolve to system discontinuities represented by intra/intersubsystem critical states