Conversely, a case of semigrammaticalness of a different sort may remedy and, at the same time, eliminate irrelevant intervening contexts in selectional rules. If the position of the trace in (99c) were only relatively inaccessible to movement, a subset of English sentences interesting on quite independent grounds does not affect the structure of the extended c-command discussed in connection with (34). A consequence of the approach just outlined is that the systematic use of complex symbols is necessary to impose an interpretation on a corpus of utterance tokens upon which conformity has been defined by the paired utterance test. Furthermore, this selectionally introduced contextual feature is rather different from nondistinctness in the sense of distinctive feature theory. We have already seen that the fundamental error of regarding functional notions as categorial is unspecified with respect to a descriptive fact.
see also: WikiPedia -- Chomskybot