Reasoning with Probabilities and Maximum Entropy: The System PIT and its Application in LEXMED

We present a theory, a system and an application for common sense reasoning based on propositional logic, the probability calculus and the concept of maximum entropy. The task of the system PIT (Probability Induction Tool) is to provide decisions under incomplete knowledge, while keeping the necessary additional assumptions as minimal and clear as possible. We therefore enrich the probability calculus by two principles which have their common source in the concept of model-quantification ([8, 17]) and find their dense representation in the well-known principle of Maximum Entropy (MAXENT [6]). As model-quantification delivers a precise semantics to MAXENT, the corresponding decisions make sense not only in our current project of medical diagnosis in LEXMED.