A model-fragment is associated with a set of time-dependent conditions and consequences; when those conditions hold, the consequences hold. While conditions and consequences are time-dependent, the participants, attributes, and quantities associated with a model-fragment are part of its definition and the associations do not change over time. Similarly, model-fragment classes are organized in a class hierarchy, and a model-fragment instance can be an instance of more than one class.
The ACTIVE predicate associates a set of conditions with a model-fragment class. A model fragment instance is active with respect to the conditions associated with a model-fragment class and a particular time. Thus, (active ?t ?mf-class ?mf-instance) holds when the conditions of the class ?mf-class, instantiated for instance ?mf-instance, are true at the time ?t.
The translation of CML forms into KIF produces axioms that determine when ACTIVE holds for particular model fragments.
(Nth-Domain Active 3 Model-Fragment) (Nth-Domain Active 1 Time-Quantity) (=> (Active ?Time ?Model-Fragment-Class ?Mf-Instance) (Subclass-Of ?Model-Fragment-Class Model-Fragment))