Where’s My Head? Definition, Data Set, and Models for Numeric Fused-Head Identification and Resolution

Where’s My Head? Definition, Data Set, and Models for Numeric Fused-Head Identification and Resolution Yanai Elazar† and Yoav Goldberg†∗ †Computer Science Department, Bar-Ilan University, Israel ∗Allen Institute for Artificial Intelligence {yanaiela,yoav.goldberg}@gmail.com Abstract We provide the first computational treatment of fused-heads constructions (FHs), focusing on the numeric fused-heads (NFHs). FHs con- structions are noun phrases in which the head noun is missing and is said to be ‘‘fused’’ with its dependent modifier. This missing information is implicit and is important for sentence understanding. The missing refer- ences are easily filled in by humans but pose a challenge for computational models. We for- mulate the handling of FHs as a two stages process: Identification of the FH construc- tion and resolution of the missing head. We explore the NFH phenomena in large cor- pora of English text and create (1) a data set and a highly accurate method for NFH iden- tification; (2) a 10k examples (1 M tokens) crowd-sourced data set of NFH resolution; and (3) a neural baseline for the NFH resolu- tion task. We release our code and data set, to foster further research into this challenging problem. 1 Introduction Many elements in language are not stated ex- plicitly but need to be inferred from the text. This is especially true in spoken language but also holds for written text. Identifying the missing in- formation and filling in the gap is a crucial part of language understanding. Consider the sentences below: (1) I’m 42 , Cercie. (2) It’s worth about two million . (3) I’ve got two months left, three at the most. (4) I make an amazing Chicken Cordon Bleu. She said she’d never had one. In Example (1), it is clear that the sentence refers to the age of the speaker, but this is not stated explicitly in the sentence. Similarly, in Example (2) the speaker discusses the worth of an object in some currency. In Example (3), the number refers back to an object already mentioned before—months. All of these examples are of numeric fused heads (NFHs), a linguistic construction that is a subclass of the more general fused heads (FHs) construction, limited to numbers. FHs are noun phrases (NPs) in which the head noun is missing and is said to be ‘‘fused’’ with its dependent modifier (Huddleston and Pullum, 2002). In the examples above, the numbers ‘42’, ‘two million’, ‘three’, and ‘one’ function as FHs, whereas their actual heads (YEARS OLD, DOLLAR, months, Chicken Cordon Bleu) are missing and need to be inferred. Although we focus on NFHs, FHs in general can occur also with other categories, such as determiners and adjectives. For example, in the following sentences: (5) Only the rich will benefit. (6) I need some screws but can’t find any . the adjective ‘rich’ refers to rich PEOPLE and the determiner ‘any’ refers to screws. In this work we focus on the numeric fused head. Such sentences often arise in dialog situations as well as other genres. Numeric expressions play an important …

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