A collection of binary predicates; a specialization of role. Each instance of predicate describing actors in events relates some instance of event to a temporal thing involved in that event (here called a participant , although the thing in question might not be playing an active role in the event). The first argument of every instance of predicate describing actors in events is constrained to be an instance of some specialization of event, and the second argument is constrained to be an instance of some specialization of thing existing stably in time.

All instances of predicate describing actors in events have actor as their Genl Preds, directly or indirectly, so that the actor slots form a kind of hierarchy. Each specialized actor slot indicates how its participant participates in the event, i.e., in what role (e.g., input, output, doer).

Actor slots are not used to indicate the time of an event's occurrence, external representations of the event, and other more remotely related things that are not directly or indirectly involved in the occurrence of the event. Time and other quantities are relevant to events but are not instances of thing existing stably in time; thus, they are related to events by some non-predicate describing actors in events predicate.

Things which are remotely related to the event -- for instance, someone who is affected by the event but doesn't exist when the event occurs -- may be related using some instance of role that does not belong to predicate describing actors in events, such as affected agent. See also role.