Bi-directional Grammars for Machine Translation

Abstract

In this paper we consider bi-directional grammars for natural languages. That is, a special class of grammars which can be used for both parsing and generation of sentences. We define the notion of "bi-directionality" and a class of general unification grammar and show that any instance of the grammar is bi-directional. We also discuss a subset of the grammar where more desirable property holds. We also consider an operational counterpart of the unification grammar, called pseudo-unification grammar, and show that similar results hold.