Local knowledge assertions in a changing world: extended abstract

When the state of the world changes due to an action performed by an agent in a multiagent system, the views of other agents, and hence their knowledge, remain unaffected. We describe such situations using a simple modal logic. Traditionally, modal logics of knowledge are interpreted over global states of the multi-agent system. When actions are incorporated into such logics, it leads to high undecidability, whereas, if we see the assertions as made by the agents in the system at their local states, we get a decidable logic, for which we also provide a complete axiomatization. Interestingly, when we consider a corresponding local temporal logic of knowledge and (linear) time, the knowledge modality represents a 'necessarily now' modality of present tense.