(documentationsubrelationEnglishLanguage "(subrelation ?REL1 ?REL2) means that every tuple of ?REL1 is also a tuple of ?REL2. In other words, if the Relation ?REL1 holds for some arguments arg_1, arg_2, ... arg_n, then the Relation ?REL2 holds for the same arguments. A consequence of this is that a Relation and its subrelations must have the same valence.")