Conditions and events are important constructs in SCR specifications. A condition is a predicate
defined on one or more state variables (a state variable is a monitored or controlled variable or
a mode class). An event occurs when a state variable changes value. A conditioned event has the
form “@T(c) WHEN d” and is defined by the expression “NOT c AND c’ and d,” where the
unprimed conditions c and d are evaluated in the “old” state, and the primed condition c’ is
evaluated in the “new” state. Informally, this expression denotes the event “predicate c becomes
true in the new state when predicate d holds in the old state.” The notation “@F(c)” denotes
the event @T(NOT c). The notation DUR(c) indicates the length of time that condition c has been
continuously true.