The class of phases, during which no changes happen.
(=> (*State ?Self)
(Exists (?Y ?Z)
(And (Situation ?Y)
(Situation ?Z)
(Context-Of ?Y ?Self)
(Exists (?A)
(And (Beginpoint ?Self ?A) (Co-Occur ?Y ?A)))
(Context-Of ?Z ?Self)
(Exists (?B)
(And (Endpoint ?Self ?B) (Co-Occur ?Z ?B)))
(Equal-But-Time ?Y ?Z))))