the interactions among participants in an event, specifically causal interactions (although there are other types of interactions among participants in an event which are subsumed under the term). Example: in The cats scratched the furniture, the cats act on the furniture, and the furniture undergoes a change of state. The causal structure of events that is expressed by a single argument structure construction in a single clause is generally in the form of a causal chain. (Sections 6.1.1, 6.1.2)