We describe a system of reversible grammar in which, given a logic-grammar specification of a natural language, two efficient PROLOGprograms are derived by an off-line compilation process: a parser and a generator for this language. The centerpiece of the system is the inversion algorithm designed to compute the generator code from the parser's PROLOG code, using the collection of minimal sets of essential arguments (MSEA) for predicates. The system has been implemented to work with Definite Clause Grammars (DCG) and is a part of an English-Japanese machine translation project currently under development at NYU's Courant Institute. .
