Definition: The expression (s STRT t) states that the temporal beginning of an event s or the beginning of the validity of a state of affairs s is determined by the second argument t, which can be another situation, a moment, or a period of time. If the second argument of the expression (x STRT y) denotes a situation (i.e. y ∈ si), then the temporal beginning of x is determined by the beginning of that time interval ty which is attached to the situation y (ty = time interval of the validity of y). In this case, the duration of y or ty must not be longer than that of situation x. The relation STRT is defined only in those cases where the first argument has a certain duration. See also FIN.