Other Formalisms

Abstract

Restriction Grammar is described in Hirschman (1986) as a “grammar-writing framework in Prolog.” The Restriction Grammar framework (Sager, 1967, 1981; Sager and Grishman 1975), following its origins in Sager’s String Grammars, consists of BNF (context-free) definitions for syntax, coupled with constraints or restrictions on the structure of the parse tree. The RG formalism automatically constructs the parse tree: thus it differs from the Metamorphosis Grammar and Definite Clause Grammar formalisms which do not, but not from later logic grammar formalisms such as Modifier Structure Grammar and Definite Clause Translation Grammars which do. The portion of the Restriction Grammar that is not context-free is specified by “restrictions” on the structure of the parse tree, rather than by augmentation of the nonterminal symbols with extra arguments as in Definite Clause Grammars.