Information Structure in Discourse

Institute for Communicating and Collaborative SystemsThe present dissertation proposes integrating Discourse Representation Theory (DRT), information structure (IS) and Combinatory Categorial Grammar (CCG) into a single framework. It achieves this by making two new contributions to computational treatment of information structure. First, it presents an uncomplicated approach to incorporating information structure in DRT. Second, it shows how the new DRT representation can be integrated into a unification-based grammar framework in a straightforward manner. We foresee the main application of the new formalism to be in spoken language systems: the approach presented here has the potential to considerably facilitate spoken language systems benefiting from insights derived from information structure. The DRT representation with information structure which is proposed in this dissertation is simpler than the previous attempts to include information structure in DRT. We believe that the simplicity of the Information-Structure-marked Discourse Representation Structure (IS-DRS) is precisely what makes it attractive and easy to use for practical tasks like determining the intonation in spoken language applications. The IS component in ISDRS covers a range of aspects of information structural semantics. A further advantage of IS-DRS is that in its case a single semantic representation is suitable for both the generation of context-appropriate prosody and automatic reasoning. A semantic representation on its own is useful for describing and analysing a language. However, it is of even greater utility if it is accompanied by a mechanism that allows one to directly infer the semantic representation from a natural language expression. We incorporated the IS-DRS into the Categorial Grammar (CG) framework, developing a unification based realisation of Combinatory Categorial Grammar, which we call Unification-based Combinatory Categorial Grammar (UCCG). UCCG inherits elements from Combinatory Categorial Grammar and Unification Categorial Grammar. The UCCG framework is developed gradually throughout the dissertation. The information structural component is included as the final step. The IS-DRSs for linguistic expressions are built up compositionally from the IS-DRSs of their sub-expressions. Feature unification is the driving force in this process. The formalism is illustrated by numerous examples which are characterised by different levels of syntactic complexity and diverse information structure. We believe that the main assets of both the IS-DRSs as well as the Unification-based Combinatory Categorial Grammar framework are their simplicity, transparency, and inherent suitability for computational implementation. This makes them an appealing choice for use in practical applications like spoken language systems

Meaning versus Grammar

This volume investigates the complicated relationship between grammar, computation, and meaning in natural languages. It details conditions under which meaning-driven processing of natural language is feasible, discusses an operational and accessible implementation of the grammatical cycle for Dutch, and offers analyses of a number of further conjectures about constituency and entailment in natural language

Predicate conjoining in Hadiyya: a head driven PS grammar

In examining certain structures of the East Cushitic language Hadiyya, this thesis, in keeping with recent trends, adopts a mono-stratal framework, framed in terms of the mathematical operation of Unification; namely Head-driven Phrase Structure Grammar (HPSG). Chapter 1 is devoted to an exposition of the model employing situation semantics. Chapter 2 discusses the categories of noun, noun phrase, and verb. The discussion centres on the basic morphological categories of Person, Number, Gender and Case, and the variety of verbal forms which are relevant to an appreciation of following chapters, and a tentative (partial) feature system is set out. Chapter 3 deals with the mono-clausal sentence, briefly expounding basic sentence types, with the focus of the chapter on the issues of subcategorisation, constituent order, "pro-drop", and agreement. Several revisions of the formalism are proposed, and a general goal formulated. Part II deals with nexus mechanisms. First is a short chapter, 4, on canonical coordination as it occurs in Hadiyya, in which an attempt is made to formalise resolution rules, and a broader, cross-linguistic look is taken at the categories of Person, Gender and Number in coordinate phrases. Some of Hadiyya's other lexical connectors are also briefly considered. In the two final chapters, both subordinative and coordinative systems are reviewed, and these chapters provide an end-focus to the study. Chapter 5, discusses the adverbial clause, and the complementation system, while Chapter 6 covers clause chaining/ serialisation, switch reference, and the encoding of simultaneous events, in which agreement and control questions are addressed. A short final chapter brings together some of the major theoretical suggestions arising.

Modeling information structure in a cross-linguistic perspective

This study makes substantial contributions to both the theoretical and computational treatment of information structure, with a specific focus on creating natural language processing applications such as multilingual machine translation systems. The present study first provides cross-linguistic findings in regards to information structure meanings and markings. Building upon such findings, the current model represents information structure within the HPSG/MRS framework using Individual Constraints. The primary goal of the present study is to create a multilingual grammar model of information structure for the LinGO Grammar Matrix system. The present study explores the construction of a grammar library for creating customized grammar incorporating information structure and illustrates how the information structure-based model improves performance of transfer-based machine translation