New Approaches to Parsing Conjunctions Using Prolog

Robert C. Berwick, Sandiway Fong

Abstract: Conjunctions are particularly difficult to parse in traditional, phrase-based grammars. This paper shows how a different representation, not based on tree structures, markedly improves the parsing problem for conjunctions. It modifies the union of phrase marker model proposed by Goodall [1984], where conjunction is considered as the linearization of a three-dimensional union of a non-tree based phrase marker representation. A PROLOG grammar for conjunctions using this new approach is given. It is far simpler and more transparent than a recent phrase-based extraposition parser conjunctions by Dahl and Mc.Cord [1984]. Unlike the Dahl and Mc.Cord or ATN SYSCONJ approach, no special trail machinery is needed for conjunction, beyond that required for analyzing simple sentences. While of comparable efficiency, the new approach unifies under a single analysis a host of related constructions: respectively sentences, right node raising, or gapping. Another advantage is that it is also completely reversible (without cuts), and therefore can be used to generate sentences.