Multi-Modal Combinatory Categorial Grammar

Multi-Modal Combinatory Categorial Grammar Jason Baldridge ICCS School of Informatics 2 Buccleuch Place University of Edinburgh Edinburgh EH8 9LW, UK ]mb@cogsci.ed.ac.uk Geert-Jan M. Kruijff Universitat des Saarlandes Computational Linguistics Lehrstuhl Uszkoreit Building 17, Postfach 15 11 50 66041 Saarbriicken, Germany gj@coli. uni—sb.de Abstract The paper shows how Combinatory Cat- egorial Grammar (CCG) can be adapted to take advantage of the extra resource- sensitivity provided by the Categorial Type Logic framework. The resulting reformulation, Multi-Modal CCG, sup- ports lexically specified control over the applicability of combinatory rules, per- mitting a universal rule component and shedding the need for language-specific restrictions on rules. We discuss some of the linguistic motivation for these changes, define the Multi-Modal CCG system and demonstrate how it works on some basic examples. We further- more outline some possible extensions and address computational aspects of Multi-Modal CCG. 1 Introduction The family of categorial grammar frameworks contains a diverse set of formalisms committed to many of the same core principles, such as compo- sitionality, a strong degree of lexicalism, and se- mantic transparency. Nonetheless, each formalism has its own characteristics with respect to the cate- gory constructors and rules of combination it em- ploys and the differing kinds of linguistic explana- tions which arise from its unique assumptions. A formalism's category constructors and com- bination rules together define its resource- sensitivity: given the resources we have (i.e. ex- pressions and their associated categories) we can, or can not, apply particular rules to form more complex expressions. It is particularly this idea of resource-sensitivity that is realized differently across different formalisms. In this paper, we explain how two prominent categorial grammar frameworks, namely Com- binatory Categorial Grammar (CCG, Steedman (2000)) and Categorial Type Logic (CTL, Mor- rill (1994); Moortgat (1997); Oehrle (to appear)), can be integrated to create a hybrid categorial framework, Multi-Modal Combinatory Categorial Grammar (Baldridge, 2002), that inherits the at- tractive properties of both. Specifically, Multi- Modal CCG retains the favorable computional as- pects of CCG whilst incorporating the approach to resource-sensitivity taken in CTL. At the theoret- ical level, we discuss how this form of resource- sensitivity enables us to replace the rather ad hoc rule-specific constraints found in CCG with a clean resource-management regime, leading to more parsimonious linguistic analyses. We also discuss some of the benefits of modalized CCG for computational processing. Although Multi-Modal CCG has the same set of rules as standard CCG, its improved resource- sensitivity enables it to have a universal rule com- ponent. It places all cross-linguistic variation in the lexicon, leading to a typological perspec- tive on grammar that not only describes, but can also make predictions about, syntactic structure: Multi-Modal CCG provides a new view on how a typological perspective can be incorporated in a lexicalized, non-transformational setting. 211 Overview. We introduce CCG in §2, and then mo- tivate the need for a revised notion of resource- sensitivity in CCG in §3. In §4, we introduce Multi-Modal CCG and present possible extensions in §5. Finally, we discuss the computational …

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