A Note on Assymmetry in Phrase Structure Grammars

I n M a t t h e w s (1963) 1 several classes of g rammars are defined and their generat ive power determined. These g rammars are defined part ia l ly by the form of their rules and par t ia l ly by the form of the derivat ions of the sentences they generate. T h a t paper shows t h a t one-way g rammars and one-way d iscont inuous g rammars are equ iva len t to context-free g rammars as defined by Chomsky (1959). This paper shows t h a t the restr ict ions on the form of the rules are no t essential ;