[...] a theory of computational lexical semantics needs to make reference to four levels of representations: [...] "Event structure" identifies the particular event type for a verb or a phrase. There are essentially three components to this structure: the primitive event type - state ("S"), process ("P") or transition ("T"); the focus of the event; and the rules for event composition.
- Pustejovsky & Boguraev (2004), Pag. 342