Application of Category Theory in Model-Based Diagnostic Reasoning

This paper discusses the use and importance of category theory in system descriptions for model-based diagnostic reasoning. We argue that category theory provides a precise and convenient conceptual language and tool to model complex systems. System descriptions are regarded as categories, in which each object is a system model and each morphism represents changes and transformations of system models. A system model is in turn viewed as a category together with some faithful functors. The category in a system model describes the structure of the device being diagnosed and the faithful functors describe the behaviour of components of the device. The mor-phism (transformation of system models) in the category as system description is a functor between categories describing structures of the device being diagnosed. We also discuss several special transformations of system models. From a system model a rst-order theory can be obtained so that existing algorithms and software systems can then be used to generate diagnosis candidates.