CHAPTER 3

The Effects of Events

Events change the state of the world. When an event occurs, some properties of the world that are false become true and some properties of the world that are true become false. This chapter is concerned with the representation of the effects of events on world properties. We discuss positive and negative effect axioms, commonly used effect axiom idioms, preconditions, and state constraints.

3.1 Positive and Negative Effect Axioms

In the event calculus, the effects of events are described by two predicates. The predicate Initiates(α, β, τ) represents that, if an event α occurs at timepoint τ, then fluent β will be true after τ. The predicate Terminates(α, β, τ) represents that, if an event α occurs at timepoint ...

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