Contextually-Dependent Lexical Semantics

Institute for Communicating and Collaborative SystemsThis thesis is an investigation of phenomena at the interface between syntax, semantics, and pragmatics, with the aim of arguing for a view of semantic interpretation as lexically driven yet contextually dependent. I examine regular, generative processes which operate over the lexicon to induce verbal sense shifts, and discuss the interaction of these processes with the linguistic or discourse context. I concentrate on phenomena where only an interaction between all three linguistic knowledge sources can explain the constraints on verb use: conventionalised lexical semantic knowledge constrains productive syntactic processes, while pragmatic reasoning is both constrained by and constrains the potential interpretations given to certain verbs. The phenomena which are closely examined are the behaviour of PP sentential modifiers (specifically dative and directional PPs) with respect to the lexical semantic representation of the verb phrases they modify, resultative constructions, and logical metonymy. The analysis is couched in terms of a lexical semantic representation drawing on Davis (1995), Jackendoff (1983, 1990), and Pustejovsky (1991, 1995) which aims to capture “linguistically relevant” components of meaning. The representation is shown to have utility for modeling of the interaction between the syntactic form of an utterance and its meaning. I introduce a formalisation of the representation within the framework of Head Driven Phrase Structure Grammar (Pollard and Sag 1994), and rely on the model of discourse coherence proposed by Lascarides and Asher (1992), Discourse in Commonsense Entailment. I furthermore discuss the implications of the contextual dependency of semantic interpretation for lexicon design and computational processing in Natural Language Understanding systems

A Perspective on PPs

This paper investigates the treatment of the semantic contribution of prepositional phrases in HPSG, with particular reference to dative prepositional phrases (PPs). Using standard syntactic and semantic tests for argument structure, it is shown that certain for- and to-dative PPs must be construed as entities at a level between pure complements and pure adjuncts. A proposal is made for the semantic integration of PPs in an HPSG framework, based on work by Kasper (1993) and van Noord and Bouma (1994). The proposed approach accommodates various syntactic and semantic properties of adjuncts and provides a way of handling dative PPs which captures generalisations about their semantic contribution across verbal heads. 1 Introduction This paper investigates the treatment of the semantic contribution of prepositional phrases in HPSG, with particular reference to dative prepositional phrases (PPs). It begins with an investigation of the status of for - and to-dative PPs in Section 2 does th..

Reduction of Lexical Redundancy via Semantically-driven Syntactic Generalisations

Syntax cannot be handled effectively in isolation from semantic factors. In this paper, a system is presented which models the syntactic phenomenon of dative alternation via its semantic basis. The system depends on a semantic representation that incorporates psycholinguistic insights about grammaticallyrelevant semantic criteria, and is implemented in an HPSG grammar in ALE. The semantic basis of the system is shown not only to lead to a more accurate and linguistically elegant model but also to aid in reducing redundancy in the base lexicon. This is accomplished through specification of lexical rules responsible for determining whether particular verbs alternate using both their syntactic and semantic properties. Furthermore, the consultation of verbal semantic features is shown to aid in prediction of the syntactic environments in which the verbs can appear. 1 Introduction Syntax cannot adequately be treated as autonomous from semantics in any reasonable NLP system. Interaction bet..

Cognitively Relevant Schemas for Knowledge Representation

this paper is to look at the psychological basis of representations used for world and lexical knowledge in NLP systems. The tacit assumption underlying this endeavour is that using a representation formalism which is psychologically valid is a Good Thing. From the perspective of many computational linguists, however, such psychological validity may not seem useful because of the vagueness associated with psychological models. Why worry about what form the representations take, they will argue, when there are systems capable of handling a wide array of tasks: anaphora resolution, quantifier scoping, query resolution, inferencing,: : : ? The reason is that there is only one system which can handle all the tasks associated with natural language -- the human mind. Current computational systems are hampered by a lack of uniformity. Issues that go beyond first order logic (modals, nonmonotonistic reasoning, etc.) are dealt with in an ad hoc way. There is no possibility of integrating the assumptions and the representations of the various systems to create a system capable of general natural language understanding. What is clearly needed is a uniform representational formalism with an explicitly defined semantics which can provide the basis for the development of systems capable of handling the range of phenomena in natural language understanding. John Sowa has argued that his conceptual graph formalism should be adopted as the worldwide standard for representation of semantic knowledge. A large part of this paper will be devoted to a description and evaluation of this formalism

What are the Characteristics of Emotional Metaphors?

Metaphors are extremely pervasive in language. They provide a powerful manner of making abstract concepts explicit. For these reasons, they are frequently utilized to describe emotional state. The current research supports the idea that metaphors used in emotional domains tend to be conventionalized. This conventionalization is what makes it possible to identify common themes in the metaphors referencing each emotional domain. The research identifies such common themes, and shows that they can provide a basis for accurate grouping of metaphors from the same domain. Contents I Background Information 3 1 Introduction 3 1.1 Emotional Expression . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 What is a Metaphor? . . . . . . . . . . . . . . . . . . . . . . . 4 1.3 Understanding Metaphor . . . . . . . . . . . . . . . . . . . . . 6 2 Linguistic/Philosophical Theories of Metaphor 8 2.1 Aristotle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2 Max Black . . . . . . ..

Lexical Limits on the Influence of Context

This paper introduces an approach to modeling the interpretation of semantically underspecified logical metonymies, such as John began the book. A distinctive feature of the theory presented is its emphasis on accounting for their behavior in discourse contexts. The approach depends on the definition of a pragmatic component which interacts in the appropriate manner with lexicosyntactic information to establish the coherence of a discourse. The infelicity of certain logical metonymy constructions in some discourses is shown to stem from the non-default nature of the lexicosyntactically determined interpretation for such constructions. The extent of the influence of contextual information from the discourse on the interpretation of logical metonymies is therefore constrained by the lexical properties of the constituents of the metonymies. Contextually-cued interpretations are shown to be unattainable when indefeasible lexical information conflicts with these interpretations

Intelligent Agents for Information Presentation: Dynamic Description of Knowledge Base Objects

Users of the World Wide Web have needs and interests which can help to determine what of the vast quantities of information available might be relevant to them. Intelligent agents might be used to select content for a particular user. However, it is also important to consider how that content is provided to a user. We suggest that this information presentation must also take into consideration the needs of a user, and discuss a set of agents which utilizes natural language generation techniques to present information in an appropriate way. In this paper we describe two systems we have built which dynamically generate descriptions of knowledge base entities, and consider the extension of the techniques used there for multilingual information presentation. We describe the notion of a phrasal lexicon as a basis for dynamic object description, and propose a model for dynamic multilingual description which builds on that notion