We have already seen that a subset of English sentences interesting on quite independent grounds may remedy and, at the same time, eliminate the traditional practice of grammarians. Notice, incidentally, that relational information is not quite equivalent to problems of phonemic and morphological analysis. With this clarification, a descriptively adequate grammar can be defined in such a way as to impose an abstract underlying order. Nevertheless, the earlier discussion of deviance does not affect the structure of the levels of acceptability from fairly high (eg (99a)) to virtual gibberish (eg (98d)). So far, the appearance of parasitic gaps in domains relatively inaccessible to ordinary extraction appears to correlate rather closely with the strong generative capacity of the theory.
see also: WikiPedia -- Chomskybot