A Heuristic Approach to Natural Language Processing

This paper is concerned with the design of a processor capable of formalizing English language descriptions of problems in the sententlal calculus. The emphasis is on the design of a system with natural language processing capabilities, but the formal languages specified are oriented to the problem context. A series of automata are specified to carry out the necessary functions. The automata identifythe premises in the problem strings~ specify the appropriate logical connectives among the premises and determine which premises are meaning-equivalent. The syntax of each automaton is defined and examples are used to illustrate their functioning. The automata accept statements in the language L1, the set of English statements of problems in the sententlal calculus. The individual premises p @ L1 are recognized by the syntax~, where ~ is chosen so that the language L2 recognized by it is a subset of L1. Furthermore, the strings in L2 are restricted to the declarative sentences. Once the premises and their logical connectives have been identified, those that are meaning-equivalent are located in two additional steps. First the L2 description of the string is mapped into a string in L3. The L3 language consists of a limited set of canonical forms that ease the problem of establishing meaning equivalence of premises. Finally, the automaton applies heuristically a sequence of problem-orlented and meaning-preserving transformations in order to establish meaning-equivalence. Two premises are taken to be meaning-equivalent if one can be deduced from the other. Otherwise~ they are taken to be not meaning-equlvalent.