Proceedings of the Annual Meeting of the Cognitive Science Society

Understanding mechanical behavior is an important part of both commonsense and expert reasoning which involves extensive spatial knowledge. A key problem in qualitative spatial reasoning is finding the right level of detail to support differing needs of reasoning methods. For example,analysis of failures may involve describing every surface imperfection; but, to gain an initial understanding of device behavior, one needs to eliminate extraneous information.People seem very good at varying their level of resolution to meet the needs of the activity being described, but in machine understanding this has proven to be a dilemma. In order to understand an artifact one needs to impose some level of abstraction, yet to obtain a sufficient level of abstraction, without omitting critical details, one needs to understand the artifact. Our solution simplifies descriptions of mechanical devices using quantitative information about qualitatively significant regions. Configuration space representation of the kinematic pairs of a mechanism serves as the underlying metric diagram to answer questions concerning contact between the components and provide the foundation for construction of a purely symbolic device description, the place vocabulary. W e explore the effect of abstracting the configuration space on condensation of the place vocabulary, showing how it makes qualitative reasoning about complex mechanisms, such as the mechanical clock, tractable. Examples shown are based on an implementation.