Analogously, a subset of English sentences interesting on quite independent grounds is, apparently, determined by the ultimate standard that determines the accuracy of any proposed grammar. So far, relational information is not subject to the requirement that branching is not tolerated within the dominance scope of a complex symbol. A consequence of the approach just outlined is that a descriptively adequate grammar can be defined in such a way as to impose a general convention regarding the forms of the grammar. Presumably, this analysis of a formative as a pair of sets of features delimits the system of base rules exclusive of the lexicon. Suppose, for instance, that the appearance of parasitic gaps in domains relatively inaccessible to ordinary extraction is to be regarded as the extended c-command discussed in connection with (34).
see also: WikiPedia -- Chomskybot