An Empirical Approach to the Interpretation of Superlatives

Proceedings of the 2006 Conference on Empirical Methods in Natural Language Processing (EMNLP 2006), pages 9–17, Sydney, July 2006. c⃝2006 Association for Computational Linguistics An Empirical Approach to the Interpretation of Superlatives Johan Bos Laboratory for Computational Linguistics Department of Computer Science University of Rome “La Sapienza” bos@di.uniroma1.it Malvina Nissim Laboratory for Applied Ontology Institute for Cognitive Science and Technology National Research Council (CNR), Rome malvina.nissim@loa-cnr.it Abstract In this paper we introduce an empirical approach to the semantic interpretation of superlative adjectives. We present a cor- pus annotated for superlatives and pro- pose an interpretation algorithm that uses a wide-coverage parser and produces se- mantic representations. We achieve F- scores between 0.84 and 0.91 for detecting attributive superlatives and an accuracy in the range of 0.69–0.84 for determining the correct comparison set. As far as we are aware, this is the first automated approach to superlatives for open-domain texts and questions. 1 Introduction Although superlative noun phrases (the nation’s largest milk producer, the most complex arms- control talks ever attempted, etc.) received consid- erable attention in formal linguistics (Szabolcsi, 1986; Gawron, 1995; Heim, 1999; Farkas and Kiss, 2000), this interest is not mirrored in com- putational linguistics and NLP. On the one hand, this seems remarkable, since superlatives are fairly frequently found in natural language. On the other hand, this is probably not that surprising, given that their semantic complexity requires deep lin- guistic analysis that most wide-coverage NLP sys- tems do not provide. But even if NLP systems incorporated linguistic insights for the automatic processing of superla- tives, it might not be of help: the formal semantics literature on superlatives focuses on linguistically challenging examples (many of them artificially constructed) which might however rarely occur in real data and would therefore have little impact on the performance of NLP systems. Indeed, no corpus-based studies have been conducted to get a comprehensive picture of the variety of configura- tions superlatives exhibit, and their distribution in real occurring data. In this paper we describe our work on the anal- ysis of superlative adjectives, which is empiri- cally grounded and is implemented into an exist- ing wide-coverage text understanding system. To get an overview of the behaviour of superlatives in text, we annotated newswire data, as well as queries obtained from search engines logs. On the basis of this corpus study, we propose, imple- ment and evaluate a syntactic and semantic analy- sis for superlatives. To the best of our knowledge, this is the first automated approach to the interpre- tation of superlatives for open-domain texts that is grounded on actual corpus-evidence and thor- oughly evaluated. Some obvious applications that would benefit from this work are question answer- ing, recognition of entailment, and more generally relation extraction systems. 2 Syntax and Semantics of Superlatives 2.1 Surface Forms In English, superlative adjectives appear in a large variety of syntactic and morphological forms. One-syllable adjectives and some two-syllable ad- jectives are directly inflected with the suffix “-est”. Some words of two syllables and all …

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