Possible World Partition Sequences: A Unifying Framework for Uncertain Reasoning

W hen we work with information from mul­ tiple sources, the formalism each employs to handle uncertainty may not be uniform. In order to be able to combine these knowl­ edge bases of different formats, we need to first establish a common basis for character­ izing and evaluating the different formalisms, and provide a semantics for the combined mechanism. A common framework can pro­ vide an infrastructure for building an inte­ grated system, and is essential if we are to understand its behavior. We present a uni­ fying framework based on an ordered par­ tition of possible worlds called partition se­ quences, which corresponds to our intuitive notion of biasing towards certain possible sce­ narios when we are uncertain of the actual situation. We show that some of the ex­ isting formalisms, namely, default logic, au­ toepistemic logic, probabilistic conditioning and thresholding (generalized conditioning), and possibility theory can be incorporated into this general framework.