Advances in the theory of representation of physical objects will be complemented by development of a general physical simulation system, and by laboratory experimentation. The research will include investigation into means to link together separate, dynamically interacting modeling systems including abstract, geometric, and dynamic modelers. The simulation system will be used in a number of applications, including designing high-level language constructs and automating robot planning. Specific investigations include high-level specification methods for physical objects and tasks (including such manipulation of non- rigid objects as knot-tying); simulating, with dynamics, the behavior of physical systems; and laboratory experiments to understand and verify ideas in gripping and mating strategies, compliant motions, and other operations in physical systems.