Lazy unification

Abstract

Unification-based NL parsers that copy argument graphs to prevent their destruction suffer from inefficiency. Copying is the most expensive operation in such parsers, and several methods to reduce copying have been devised with varying degrees of success. Lazy Unification is presented here as a new, conceptually elegant solution that reduces copying by nearly an order of magnitude. Lazy Unification requires no new slots in the structure of nodes, and only nominal revisions to the unification algorithm.