The sentence {tt (proper-subset $tau_1$ $tau_2$)} is true if the set denoted by $tau_1$ is a subset of the set denoted by $tau_2$ but not vice-versa.Notes:
- Source: KIF Version 3.0 Specification
(=> (Proper-Subset ?S1 ?S2) (Not (Subset ?S2 ?S1))) (=> (Proper-Subset ?S1 ?S2) (Subset ?S1 ?S2))
(<=> (Proper-Subset ?S1 ?S2)
(And (Subset ?S1 ?S2) (Not (Subset ?S2 ?S1))))
(Exists (?U)
(And (Bounded ?U)
(Not (Empty ?U))
(Forall (?X)
(=> (Member ?X ?U)
(Exists (?Y)
(And (Member ?Y ?U)
(Proper-Subset ?X ?Y)))))))