 The confusion has led to focused study of these constructions, and their impact on the theory of grammar may be great since they appear to challenge the initial binary division of the sentence (S) into a subject noun phrase (NP) and a predicate verb phrase (VP) (S → NP VP), this division being at the core of all phrase structure grammars (as opposed to dependency grammars, which do not acknowledge the binary division).Inverse copular constructions involve nouns and noun phrases, but they do not allow the post-copula nominal to be a personal pronoun