Deixis, binding and presupposition

Dynamic semantic accounts of presupposition have proven to quite successful improvements over earlier theories. One great advance has been to link presupposition and anaphora together (van der Sandt 92, Geurts 95), an approach that extends to integrate bridging and other discourse phenomena (Asher and Lascarides 1998a,b). In this extended anaphoric account, presuppositions attach, like assertions, to the discourse context via certain rhetorical relations. These discourse attachments constrain accommodation and help avoid some infelicitous predictions of standard accounts of presupposition. Further, they have interesting and complex interactions with underspecified conditions that are an important feature of the contributions of most presupposition triggers. Deictic uses of definites, on the other hand, seem at first glance to fall outside the purview of an anaphoric theory of presupposition. There seems to be little that a discourse based theory would have to say. I will argue, however, that a discourse based account can capture how these definites function in conversation. In particular such accounts can clarify the interaction between the uses of such deictic definites and various conversational moves. At least some deictic uses of definites generate presuppositions that are bound to the context via a rhetorical function that I'll call unchoring, which if successful entails a type of knowing how. If this anchoring function is accepted, then the acceptors know how to locate the referent of the definite in the present context. I'll concentrate here just on definites that refer to spatial locations, where the intuitions about anchoring are quite clear. But I think that this view extends to other deictic uses of definites and has ramifications for an analysis of de re attitudes as well

Presupposition projection as proof construction

Even though Van der Sandt's presuppositions as anaphora approach is empirically successful, it fails to give a formal account of the interaction between world-knowledge and presuppositions. In this paper, an algorithm is sketched which is based on the idea of presuppositions as anaphora. It improves on this approach by employing a deductive system, Constructive Type Theory (CTT), to get a formal handle on the way world-knowledge influences presupposition projection. In CTT, proofs for expressions are explicitly represented as objects. These objects can be seen as a generalization of DRT's discourse markers. They are useful in dealing with presuppositional phenomena which require world-knowledge, such as Clark's bridging examples and Beaver's conditional presuppositions

An Incremental Model of Anaphora and Reference Resolution Based on Resource Situations

Notwithstanding conclusive psychological and corpus evidence that at least some aspects of anaphoric and referential interpretation take place incrementally, and the existence of some computational models of incremental reference resolution, many aspects of the linguistics of incremental reference interpretation still have to be better understood. We propose a model of incremental reference interpretation based on Loebner’s theory of definiteness and on the theory of anaphoric accessibility via resource situations developed in Situation Semantics, and show how this model can account for a variety of psychological results about incremental reference interpretation

Presuppositions in Context: Constructing Bridges

About the book: The First International and Interdisciplinary Conference on Modelling and Using Context, Rio de Janeiro, January 1997, gave rise to the present book, which contains a selection of the papers presented there, thoroughly refereed and revised. The treatment of contexts as bona fide objects of logical formalisation has gained wide acceptance, following the seminal impetus given by McCarthy in his Turing Award address. The field of natural language offers a particularly rich variety of examples and challenges to researchers concerned with the formal modelling of context, and several chapters in the volume deal with contextualisation in the setting of natural language. Others adopt a purely formal-logical viewpoint, seeking to develop general models of even wider applicability. The 12 chapters are organised in three groups: formalisation of contextual information in natural language understanding and generation, the application of context in mechanised reasoning domains, and novel non-classical logics for contextual application

The role of semantics in spoken dialogue translation systems

In this paper, we consider the role of semantics in the spoken dialogue translation systems. We begin by looking at some of the key properties of an existing spoken dialogue system, namely the sundial system which provides flight and train information over the telephone, and how these properties affect the design methodology and functionality of spoken translation systems. These properties include the effects of speech processing, designing the system to meet the needs of users, and an analysis model which clearly separates the linguistic, conceptual, pragmatic and task levels. In this model many task functionalities are dependent upon, and sometimes realizable by, the semantic and pragmatic analysis components. Central to this approach, is the use of underspecified semantic representations which are further specified as and when required by domain and/or task analysis. This model can be applied in the development of spoken translation systems with two important effects: monolingual semantic and pragmatic analysis can be carried out by processes independent of, but correlated with, the (translation) function of the system; and the main functions of the transfer processes is to further specifying the representations for the target language and to deal with mismatches between source and target language representations. We illustrate this approach with semantic analyses of German utterances required for translation in the verbmobil spoken dialogue translation system

A perceptually based computational framework for the interpretation of spatial language

The goal of this work is to develop a semantic framework to underpin the development of natural language (NL) interfaces for 3 Dimensional (3-D) simulated environments. The thesis of this work is that the computational interpretation of language in such environments should be based on a framework that integrates a model of visual perception with a model of discourse. When interacting with a 3-D environment, users have two main goals the first is to move around in the simulated environment and the second is to manipulate objects in the environment. In order to interact with an object through language, users need to be able to refer to the object. There are many different types of referring expressions including definite descriptions, pronominals, demonstratives, one-anaphora, other-expressions, and locative-expressions Some of these expressions are anaphoric (e g , pronominals, oneanaphora, other-expressions). In order to computationally interpret these, it is necessary to develop, and implement, a discourse model. Interpreting locative expressions requires a semantic model for prepositions and a mechanism for selecting the user’s intended frame of reference. Finally, many of these expressions presuppose a visual context. In order to interpret them this context must be modelled and utilised. This thesis develops a perceptually grounded discourse-based computational model of reference resolution capable of handling anaphoric and locative expressions. There are three novel contributions in this framework a visual saliency algorithm, a semantic model for locative expressions containing projective prepositions, and a discourse model. The visual saliency algorithm grades the prominence of the objects in the user's view volume at each frame. This algorithm is based on the assumption that objects which are larger and more central to the user's view are more prominent than objects which are smaller or on the periphery of their view. The resulting saliency ratings for each frame are stored in a data structure linked to the NL system’s context model. This approach gives the system a visual memory that may be drawn upon in order to resolve references. The semantic model for locative expressions defines a computational algorithm for interpreting locatives that contain a projective preposition. Specifically, the prepositions in front of behind, to the right of, and to the left of. There are several novel components within this model. First, there is a procedure for handling the issue of frame of reference selection. Second, there is an algorithm for modelling the spatial templates of projective prepositions. This algonthm integrates a topological model with visual perceptual cues. This approach allows us to correctly define the regions described by projective preposition in the viewer-centred frame of reference, in situations that previous models (Yamada 1993, Gapp 1994a, Olivier et al 1994, Fuhr et al 1998) have found problematic. Thirdly, the abstraction used to represent the candidate trajectors of a locative expression ensures that each candidate is ascribed the highest rating possible. This approach guarantees that the candidate trajector that occupies the location with the highest applicability in the prepositions spatial template is selected as the locative’s referent. The context model extends the work of Salmon-Alt and Romary (2001) by integrating the perceptual information created by the visual saliency algonthm with a model of discourse. Moreover, the context model defines an interpretation process that provides an explicit account of how the visual and linguistic information sources are utilised when attributing a referent to a nominal expression. It is important to note that the context model provides the set of candidate referents and candidate trajectors for the locative expression interpretation algorithm. These are restncted to those objects that the user has seen. The thesis shows that visual salience provides a qualitative control in NL interpretation for 3-D simulated environments and captures interesting and significant effects such as graded judgments. Moreover, it provides an account for how object occlusion impacts on the semantics of projective prepositions that are canonically aligned with the front-back axis in the viewer-centred frame of reference

Vagueness and referential ambiguity in a large-scale annotated corpus

In this paper, we argue that difficulties in the definition of coreference itself contribute to lower inter-annotator agreement in certain cases. Data from a large referentially annotated corpus serves to corroborate this point, using a quantitative investigation to assess which effects or problems are likely to be the most prominent. Several examples where such problems occur are discussed in more detail, and we then propose a generalisation of Poesio, Reyle and Stevenson’s Justified Sloppiness Hypothesis to provide a unified model for these cases of disagreement and argue that a deeper understanding of the phenomena involved allows to tackle problematic cases in a more principled fashion than would be possible using only pre-theoretic intuitions

Discourse structure and information structure : interfaces and prosodic realization

In this paper we review the current state of research on the issue of discourse structure (DS) / information structure (IS) interface. This field has received a lot of attention from discourse semanticists and pragmatists, and has made substantial progress in recent years. In this paper we summarize the relevant studies. In addition, we look at the issue of DS/ISinteraction at a different level—that of phonetics. It is known that both information structure and discourse structure can be realized prosodically, but the issue of phonetic interaction between the prosodic devices they employ has hardly ever been discussed in this context. We think that a proper consideration of this aspect of DS/IS-interaction would enrich our understanding of the phenomenon, and hence we formulate some related research-programmatic positions

Presupposition Resolution With Discourse Information Structures

An approach to resolving a number of presuppositional phenomena, including definite descriptions and pronominal anaphora, is described within the larger context of an architecture for query-based, task-oriented human/computer dialogue. The model of discourse context employed assumes that discourse structure is organized around a stack of questions under discussion, which plays an important role in narrowing the search space for referents and other presupposed information. The algorithms of individual presuppositional operators for maintaining discourse structures are presented and illustrated in several example dialogues in which human users interact with an agent in order to make hotel reservations. The overall architecture is compared to SDRT (Segmented Discourse Representation Theory), in terms of efficiency and ease of implementation