RELPRON: A Relative Clause Composition Dataset for Compositional Distributional Semantics

Abstract

This article introduces RELPRON, a large dataset of subject and object relative clauses, for the evaluation of methods in compositional distributional semantics. RELPRON targets an intermediate level of grammatical complexity between content-word pairs and full sentences. The task involves matching terms, e.g. 'wisdom', with representative properties, e.g. 'quality that experience teaches'. A unique feature of RELPRON is that it is built from attested properties, but without the need for them to appear in relative clause format in the source corpus. The article also presents some initial experiments on RELPRON, using a variety of composition methods, from simple baselines, through to arithmetic operators on vectors, and finally more complex methods in which argument-taking words are represented as tensors. The latter methods are based on the Categorial framework, which is described in detail.  The results show that vector addition is difficult to beat --- in line with the existing literature --- but that an implementation of the Categorial framework based on the Practical Lexical Function model is able to match the performance of vector addition. The article finishes with an in-depth analysis of RELPRON, showing how results vary across subject and object relative clauses, across the different head nouns, and how the methods perform on the subtasks necessary for capturing relative clause semantics, as well as a qualitative analysis highlighting some of the more common errors. Our hope is that the competitive results presented here, in which the best systems are on average ranking one out of every two properties correctly for a given term, will inspire new approaches to the RELPRON ranking task and other linguistically interesting constructions.