We have defined the 'categorial component' as the system of rewriting rules of the base - that is, the system of base rules exclusive of the lexicon and the subcategorization rules that we, for the present, regard as belonging to the lexicon. The rules of categorial component carry out two quite separate functions: they define the system of grammatical relations, and they determine the ordering of elements in deep structures.
- Chomsky (1969), a pag.123