 In the DEL study of belief change, situations involving the beliefs of multiple agents are represented using a variation of basic Kripke models called plausibility models. Static belief change is interpreted as conditionalization in these models: without changing the model (i.e., the situation), we see what the agent would believe conditional on the incoming information. This will be explained in detail in a moment. Dynamic belief change involves transforming plausibility models: after introducing plausibility model-compatible action models, we use model operators defined from these “plausibility action models” to describe changes in the plausibility model (i.e., the situation) itself. 