Experience with an Easily Computed Metric for Ranking Alternative Parses

Abstract

This chapter describes a metric that can be easily computed during either bottom-up or top-down construction of a parse tree for ranking the desirability of alternative parses. In its simplest form, the metric tends to prefer trees in which constituents are pushed as far down as possible, but by appropriate modification of a constant in the formula other behavior can be obtained also. The chapter includes an introduction to the Epistle system developed at IBM Research and a discussion of the results of using this metric with that system. (Epistle has evolved into the Critique text-critiquing system.)