Planning multisentential English text using communicative acts

The goal of this research is to develop explanation presentation mechanisms for knowledge based systems which enable them to define domain terminology and concepts, narrate events, elucidate plans, processes, or propositions and argue to support a claim or advocate action. This requires the development of devices which select, structure, order and then linguistically realize explanation content as coherent and cohesive English text. With the goal of identifying generic explanation presentation strategies, a wide range of naturally occurring texts were analyzed with respect to their communicative sttucture, function, content and intended effects on the reader. This motivated an integrated theory of communicative acts which characterizes text at the level of rhetorical acts (e.g., describe, define, narrate), illocutionary acts (e.g., inform, request), and locutionary acts (e.g., ask, command). Taken as a whole, the identified communicative acts characterize the structure, content and intended effects of four types of text: description, narration, exposition, argument. These text types have distinct effects such as getting the reader to know about entities, to know about events, to understand plans, processes, or propositions, or to believe propositions or want to perform actions. In addition to identifying the communicative function and effect of text at multiple levels of abstraction, this dissertation details a tripartite theory of focus of attention (discourse focus, temporal focus, and spatial focus) which constrains the planning and linguistic realization of text. To test the integrated theory of communicative acts and tripartite theory of focus of attention, a text generation system TEXPLAN (Textual EXplanation PLANner) was implemented that plans and linguistically realizes multisentential and multiparagraph explanations from knowledge based systems. The communicative acts identified during text analysis were formalized as over sixty compositional and (in some cases) recursive plan operators in the library of a hierarchical planner. Discourse, temporal, and spatial focus models were implemented to track and use attentional information to guide the organization and realization of text. Because the plan operators distinguish between the communicative function (e.g., argue for a proposition) and the expected effect (e.g., the reader believes the proposition) of communicative acts, the system is able to construct a discourse model of the structure and function of its textual responses as well as a user model of the expected effects of its responses on the reader's knowledge, beliefs, and desires. The system uses both the discourse model and user model to guide subsequent utterances. To test its generality, the system was interfaced to a variety of domain applications including a neuropsychological diagnosis system, a mission planning system, and a knowledge based mission simulator. The system produces descriptions, narrations, expositions, and arguments from these applications, thus exhibiting a broader range of rhetorical coverage than previous text generation systems

Machine humour: An implemented model of puns

Institute for Communicating and Collaborative SystemsThis thesis describes a formal model of a subtype of humour, and the implementation of that model in a program that generates jokes of that subtype. Although there is a great deal of literature on humour in general, very little formal work has been done on puns, and none has been implemented. All current linguistic theories of humour are over-general and not falsifiable. Our model, which is specific, formal, implemented and evaluated, makes a significant contribution to the field. Punning riddles are our chosen subtype of verbal humour, for several reasons. They are very common, they exhibit certain regular structures and mechanisms, and they have been studied previously by linguists. Our model is based on our extensive analysis of large numbers of punning riddles, taken from children's joke books. The implementation of the model, JAPE (Joke Analysis and Production Engine), generates punning riddles, from a humour independent lexicon. Pun generation requires much less world knowledge than pun comprehension, making it feasible for implementation. To support our claim that all of JAPE's output is punning riddles, we conducted an evaluatory experiment. We took JAPE texts, human-generated texts, nonsense non-jokes and sensible non-jokes, and asked joke experts to evaluate them. For joke experts, we used 8-11 year old children, since psychological research suggests that this age group enjoys, and can recognize, punning riddles better than other age groups. The results showed that JAPE's output texts are, in fact, recognizably jokes. The evaluation showed that our model adequately describes a significant subtype of verbal humour. We believe that this model can now be expanded to cover puns in general, as well as other types of linguistic humour

Evidence and Formal Models in the Linguistic Sciences

This dissertation contains a collection of essays centered on the relationship between theoretical model-building and empirical evidence-gathering in linguistics and related language sciences. The first chapter sets the stage by demonstrating that the subject matter of linguistics is manifold, and contending that discussion of relationships between linguistic models, evidence, and language itself depends on the subject matter at hand. The second chapter defends a restrictive account of scientific evidence. I make use of this account in the third chapter, in which I argue that if my account of scientific evidence is correct, then linguistic intuitions do not generally qualify as scientific evidence. Drawing on both extant and original empirical work on linguistic intuitions, I explore the consequences of this conclusion for scientific practice. In the fourth and fifth chapters I examine two distinct ways in which theoretical models relate to the evidence. Chapter four looks at the way in which empirical evidence can support computer simulations in evolutionary linguistics by informing and constraining them. Chapter five, on the other hand, probes the limits of how models are constrained by the data, taking as a case study empirically-suspect but theoretically-useful intentionalist models of meaning

Semantic study of spatial and temporal expressions in English

An investigation into the semantic systems underlying spatial and temporal expressions in confronted with two major problems: the interplay of contextual factors in determining the interpretation of particular expressions and the inter-relations between the two semantic systems. The first of these in a recurrent theme through- out the dissertation; the second underlies its organization and orientation. We begin, in Chapter 2, with a discussion of three recent studies on the semantics of spatial expressions in English. The conclusion is reached that more explicit attention must be given to the role of the intra-sentential context and, in particular, to the kind of situation being described by the sentence in which the expression occurs. We also recognize the need to give an explicit and comprehensive characterization of the notion of a journey, which latter in prerequisite to an understanding of such functional semantic elements an SOURCE, GOAL, PATH. Chapter 3 in devoted to the semantic analysis of static uses of locational and directional expressions. A tri-partite distinction is made between direct locational expressions (e.g. 'at the Post office) a semi-direct locational expressions (e.g. in front of the Post office"), and indirect locational expressions (e.g. above the Post office), Static directional expressions (e.g. towards the post office') are subsumed within indirect locational expressions. The orientational properties of the speaker/observer are found to be crucial to the analysis of the meanings of semi-direct and indirect locational expressions. Chapter 4 sets forth the historical background of the localist, hypothesis and surveys more recent arguments of a semantic and syntactic nature which have been given in support of it. According to the hypothesis, grammatical relations or functions, whether abstract or concrete, are ultimately describable in terms of spatial notions. The thesis of localism in set within a more encompassing theory of egocentric and anthropocentric extension operative throughout the language. Chapter 5 enumerates and discusses the major contextual elements within the sentence which interact with the co-occurrence and interpretation potential of temporal adverbial. These comprise tense, the progressive form, negation, spatial adverbials, referential proportion of the noun phrases and lexical properties of the verb. Chapter 6 redirects the focus to aspectual categories and to different kinds of propositions which some of the other contextual elements isolated in Chapter 5 participate in defining and with reference to which generalizations regarding co-occurrence and interpretations become statable. The logico-philocaphical tradition with respect to verb classification is surveyed and then the linguistic literature an aspect, aktionsartan, and verb classes. It is suggested that a distinction be made between aspect, aktionsartan, and proposition types, what is common to these three categories being the role played by the concepts of existential status and change of existential status in their characterizations. Chapter 7 begins with an inforual characterization of a journey, first in its most concrete and idealized manifestation an a point moving from one point to another. The extension of locational relations, direction, directed movementl, and journey to more abstract domains, including most importantly the existential and the temporal, is explored. The notion of existential location in incorporated into a descriptive apparatus for the semantics of expressions of physical extension in one dimension. This same notion also leads to a natural interpretation of negation, quantification, aspect and aktionearten and provides for a precise fomulation of, a. journey. A more generalized characterization of a journey in given which takes into account the extension of the moving object. A localist classification of proposition types in proposed. Chapter,. 8 applies the framework developed in Chapter 7 to the analysis of tense and to the description of two selected note of CkYT , lov%seadverbials: , (I) 'still! # Oyetlp IalreadyIq 13353M= and and (2) *until* and 'since** 'Chapter 9 onumerates, the main findings of the investigation* to the kind of situation being doscribed by the sentence in which thO OxPr0, 8sion occurs* We also recognize the need to give an explicit and comprehensive characterization of the notion of a journeyp which latter in prerequisite to an understanding of such functional semantic elements an SOURCE9G OAL9P ATH. Chapter 3 in devoted to the semantic analysis of static us* of locational and directional expressions. A tri. partits distinction is made between direct locational, expressions (soge 'at the Post office)q semi-direct locational expressions (sege Un frOist of the I)Oat office"), and indirect locational expressions (soge labove the Post offiest), Static directional expressions (*4, ge #towards the post office') are subsumed within indirect locational expressionse The orientational properties of the speaker/observer are found U) be crucial to the analysis of the meanings of semi. -direct and indirect locational, expressions. Chapter 4 sets forth the historical background of the localist, (ii) hypothesis and surveys nors, recent arguments of a semantic and syntactic nature which have been given in support of it* According to the hypothesis# grammatical relations or functionsp whether abstract or concretes are ultimately describable in terms of spatial notionse The thesis of localism in set within a more encompassing theory of egocentric and anthropocentric extension operative throughout the language. Chapter 5 enumerates and discusses the major contextual elements within the sentence which interact with the co-occurrence and interpretation potential of temporal adverbial@* These comprise tonset the progressive forms negationg spatial adverbialsq referential proportion of the noun phrases and lexical properties of the verb* Chapter 6 redirects the focus to aspectual categories and tw different kinds of propositions which some of the other contextual elements isolated in Chapter 5 participate in defining and with reference to which generalizations regarding oo-occurrence and interpretations become statablee The logico-philocaphical tradition with respect to verb classification is surveyed and then the linguistic literature an aspectq aktionsartang and verb classes* It in suggested that a distinction be made between aspootp aktionsarteng and proposition types, what in coitmon to these three categories being the role played by the concepts of existential status and change of existential status in their characterizations. Chapter 7 begins with an inforual characterization of a journeyp first in its most concrete and idealized manifestation an a point moving from one point to another* The extension of locatiOnal roletionag directiong directed movementl, and journey to more abstract domainag including most importantly the existential and the temporal* is *xplorede The notion of existential location in incorporated (iii) into a descriptive apparatus for the semantics of expressions of physical extension in one dimension* This same notion also leads to a natural interpretation of negationg quantificationg aspect and aktionearten and provides for a precise fomulation of, a. JournOY9 A more generalized characterization of a journey in given which takes into account the extension of the moving objooto A 10cali8t classification of proposition types in proposed* Chapter,. 8 applies the framework developed in Chapter 7 to the analysis of tans* and to the description of two selected note of CkYT , lov%seadverbials: , (I) 'still! # Oyetlp IalreadyIq 13353M= and and (2) *until* and 'since** 'Chapter 9 onumerates, the main findings of the investigation