Implementing a Multi-Valued Symbolic Model Checker


Multi-valued logics support the explicit modeling of uncertainty and disagreement by allowing additional truth values in the logic. Such logics can be used for verification of dynamic properties of systems even where complete, agreed upon models of the system are not available. In this paper, we present an implementation of a symbolic model checker for multi-valued temporal logics. The model checker works for any multi-valued logic whose truth values form a quasi-boolean lattice. Our models are generalized Kripke structures, where both atomic propositions and transitions between states may take any of the truth values of a given multi-valued logic. Properties to be model checked are expressed in CTL, generalized with a multi-valued semantics. The design of the model checker is based on the use of MDDs, a multi-valued extension of Binary Decision Diagrams. We describe MDDs and their use in the model checker. We also give its theoretical time complexity and some preliminary empirical performance data.