View-based explicit knowledge

In the information-based definition of knowledge, an agent is said to know alpha at a state s if alpha is true in all states that look the same as a to that agent. However, in systems where an agent's View of the system is partial, even if a state s' may be logically indistinguishable from a state a, s' may not be visible from s. For instance, in a distributed system, all global states in which the agent's local state does not change look the same to that agent, but this set of global states may not be accessible because the agent may not even be aware of the existence of many agents in the network. We propose a logic of explicit knowledge built on agents' views and show it to be decidable. (C) 1999 Elsevier Science B.V. All rights reserved.