Invited Talk: Slacker Semantics: Why Superficiality, Dependency and Avoidance of Commitment can be the Right Way to Go

Proceedings of the 12th Conference of the European Chapter of the ACL, pages 1–9, Athens, Greece, 30 March – 3 April 2009. c⃝2009 Association for Computational Linguistics Slacker semantics: why superficiality, dependency and avoidance of commitment can be the right way to go Ann Copestake Computer Laboratory, University of Cambridge 15 JJ Thomson Avenue, Cambridge, UK aac@cl.cam.ac.uk Abstract This paper discusses computational com- positional semantics from the perspective of grammar engineering, in the light of ex- perience with the use of Minimal Recur- sion Semantics in DELPH-IN grammars. The relationship between argument index- ation and semantic role labelling is ex- plored and a semantic dependency nota- tion (DMRS) is introduced. 1 Introduction The aim of this paper is to discuss work on com- positional semantics from the perspective of gram- mar engineering, which I will take here as the de- velopment of (explicitly) linguistically-motivated computational grammars. The paper was written to accompany an invited talk: it is intended to pro- vide background and further details for those parts of the talk which are not covered in previous pub- lications. It consists of an brief introduction to our approach to computational compositional seman- tics, followed by details of two contrasting topics which illustrate the grammar engineering perspec- tive. The first of these is argument indexing and its relationship to semantic role labelling, the second is semantic dependency structure. Standard linguistic approaches to compositional semantics require adaptation for use in broad- coverage computational processing. Although some of the adaptations are relatively trivial, oth- ers have involved considerable experimentation by various groups of computational linguists. Per- haps the most important principle is that semantic representations should be a good match for syn- tax, in the sense of capturing all and only the in- formation available from syntax and productive morphology, while nevertheless abstracting over semantically-irrelevant idiosyncratic detail. Com- pared to much of the linguistics literature, our analyses are relatively superficial, but this is essen- tially because the broad-coverage computational approach prevents us from over-committing on the basis of the information available from the syntax. One reflection of this are the formal techniques for scope underspecification which have been de- veloped in computational linguistics. The im- plementational perspective, especially when com- bined with a requirement that grammars can be used for generation as well as parsing, also forces attention to details which are routinely ignored in theoretical linguistic studies. This is particularly true when there are interactions between phenom- ena which are generally studied separately. Fi- nally, our need to produce usable systems disal- lows some appeals to pragmatics, especially those where analyses are radically underspecified to al- low for syntactic and morphological effects found only in highly marked contexts.1 In a less high-minded vein, sometimes it is right to be a slacker: life (or at least, project funding) is too short to implement all ideas within a grammar in their full theoretical glory. Often there is an easy alternative which conveys the necessary informa- tion to a consumer of the semantic representations. Without …

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