Context-free grammars, far from having insufficient expressive power for the description of human fan K uages, may he overly powerful, along three dimensions; (i) weak generative capacity: there exists an interesting proper subset of the CFL's, the profligate CFL's, within which no human language appears to fall; (2) strong generative capacity: human l a n g u a g e s can be a p p r o p r i a t e l y d e s c r i b e d i n terms of a proper subset of the CF-PSG's, namely those with the.
