Conversely, a case of semigrammaticalness of a different sort is not quite equivalent to a parasitic gap construction. We have already seen that the descriptive power of the base component is not to be considered in determining the system of base rules exclusive of the lexicon. Suppose, for instance, that the theory of syntactic features developed earlier can be defined in such a way as to impose an important distinction in language use. We will bring evidence in favor of the following thesis: most of the methodological work in modern linguistics is rather different from the requirement that branching is not tolerated within the dominance scope of a complex symbol. On our assumptions, the natural general principle that will subsume this case cannot be arbitrary in the ultimate standard that determines the accuracy of any proposed grammar.
see also: WikiPedia -- Chomskybot