Dynamic Knowledge Logic H.P. van Ditmarsch Abstract: Modelling the epistemic dynamics of multiagent systems currently gets much attention from the research community. Contrary to most approaches, we restrict ourselves to S 5 models. We propose a language KT of knowledge action types and a derived language KA of knowledge actions. Basic to our approach is the concept of local interpretation, where `local' means: only for the agents involved in that action. The language can be fruitfully applied to describe actions in knowledge games.