A Logic for Reasoning about Upper Probabilities
  We present a propositional logic to reason about the uncertainty of events, where the uncertainty is modeled by a set of probability measures assigning an interval of probability to each event. We give a sound and complete axiomatization for the logic, and show that the satisfiability problem is NP-complete, no harder than satisfiability for propositional logic. 
Joseph Y. Halpern, Riccardo Pucella
cs.AI cs.LO