If the position of the trace in (99c) were only relatively inaccessible to movement, the speaker-hearer's linguistic intuition can be defined in such a way as to impose problems of phonemic and morphological analysis. Presumably, the fundamental error of regarding functional notions as categorial is not to be considered in determining nondistinctness in the sense of distinctive feature theory. This suggests that relational information is, apparently, determined by a general convention regarding the forms of the grammar. Comparing these examples with their parasitic gap counterparts in (96) and (97), we see that this selectionally introduced contextual feature does not affect the structure of the traditional practice of grammarians. It must be emphasized, once again, that the notion of level of grammaticalness is not quite equivalent to the extended c-command discussed in connection with (34).
see also: WikiPedia -- Chomskybot