Knowledge updates: Semantics and complexity issues

We then investigate the computational complexity of model checking for knowledge update. We first show that in general the model checking for knowledge update is Σ2P-complete. We then identify a subclass of knowledge update problems that has polynomial time complexity for model checking. We point out that some important knowledge update problems belong to this subclass. We further address another interesting subclass of knowledge update problems for which the complexity of model checking is NP-complete.