The knowledge necessary for event detection includes a good model of the environment around the agent, so that differences between what the sensors report and what the agent believes can be meaningful. An agent also needs to know the organization of the group of which it is a part, including its own and others' responsibilities and commitments to actions (i.e., their intentions [e.g.,]pgp,georgeff:ingrand:88). This allows it to predict the likely impact of features of the environment (or itself, or others) that it detects on its and others' actions and plans. For event notification messages, the agent needs to know how reliable the other agent is, not only with respect to the sender's processing and sensor abilities, but also its beliefs and knowledge about the agent and the group. The agent also needs to maintain a history of past sensor information, beliefs, and so forth, so that trends and intermittent events can be detected (e.g., power slowly failing).