Nicholas Asher

Intentions are an important concept in Artificial Intelligence and Cognitive Science. We present a formal theory of intentions and beliefs based on Discourse Representation Theory that captures many of their important logical properties. Unlike possible worlds approaches, this theory does not assume that agents are perfect reasoners, and gives a realistic view of their internal architecture; unlike most representational approaches, it has an objective semantics, and does not rely on an ad hoc labeling of the internal states of agents. We describe a minimal logic for intentions and beliefs that is sound and complete relative to our semantics. We discuss several additional axioms, and the constraints on the models that validate them

This essay lays out a view of linguistic content in which discourse context plays an essential role. It provides a role for sentential content by using underspecification but argues that discourse level phenomena are essential not only to determining content but even grammaticality judgments in certain cases. It is thus argued that the traditional view which separates very strictly the areas of semantics — a context insensitive notion of meaning — and pragmatics — a non linguistic notion of speaker meaning — is inaccurate. In this line of thought, the paper pays a particular attention to hidden indexicals, anaphora and tense. The necessity of taking into account discursive parameters in order to solve semantic indeterminacy in such cases is argued for.

In this paper, we offer a novel analysis of bridging, paying particular attention to definite descriptions. We argue that extant theories don't do justice to the way different knowledge resources interact. In line with Hobbs (1979), we claim that the rhetorical connections between the propositions introduced in the text play an important part. But our work is distinct from his in that we model how this source of information interacts with compositional and lexical semantics. We formalize bridging in a framework known as SDRT (Asher 1993). We demonstrate that this provides a richer, more accurate interpretation of definite descriptions than has been offered so far

In this paper, we show how game theoretic work on conversation combined with a theory of discourse structure provides a framework for studying interpretive bias and how bias affects the production and interpretation of linguistic content. We model the influence of author bias on the discourse content and structure of the author’s linguistic production and interpreter bias on the interpretation of ambiguous or underspecified elements of that content and structure. Interpretive bias is an essential feature of learning and understanding but also something that can be exploited to pervert or subvert the truth. We develop three types of games to understand and to analyze a range of interpretive biases, the factors that contribute to them, and their strategic effects.

Most models of rational action assume that all possible states and actions are pre-defined and that preferences change only when beliefs do. But several decision and game problems lack these features, calling for a dynamic model of preferences: preferences can change when unforeseen possibilities come to light or when there is no specifiable or measurable change in belief. We propose a formally precise dynamic model of preferences that extends an existing static model. Our axioms for updating preferences preserve consistency while minimising change, like Hansson’s :1–28, 1995). But unlike prior models of preference change, ours supports default reasoning with partial preference information, which is essential to handle decision problems where the decision tree isn’t surveyable. We also show that our model avoids problems for other models of preference change discussed in Spohn

When two people engage in a conversation, knowingly or unknowingly, they are playing a game. Players of such games have diverse objectives, or winning conditions: an applicant trying to convince her potential employer of her eligibility over that of a competitor, a prosecutor trying to convict a defendant, a politician trying to convince an electorate in a political debate, and so on. We argue that infinitary games offer a natural model for many structural characteristics of such conversations. We call such games message exchange games, and we compare them to existing game theoretic frameworks used in linguistics—for example, signaling games—and show that message exchange games are needed to handle non-cooperative conversation. In this paper, we concentrate on conversational games where players’ interests are opposed. We provide a taxonomy of conversations based on their winning conditions, and we investigate some essential features of winning conditions like consistency and what we call rhetorical cooperativity. We show that these features make our games decomposition sensitive, a property we define formally in the paper. We show that this property has far-reaching implications for the existence of winning strategies and their complexity. There is a class of winning conditions for which message exchange games are equivalent to Banach- Mazur games, which have been extensively studied and enjoy nice topological results. But decomposition sensitive goals are much more the norm and much more interesting linguistically and philosophically.

This essay lays out a view of linguistic content in which discourse context plays an essential role. It provides a role for sentential content by using underspecification but argues that discourse level phenomena are essential not only to determining content but even grammaticality judgments in certain cases. It is thus argued that the traditional view which separates very strictly the areas of semantics — a context insensitive notion of meaning — and pragmatics — a non linguistic notion of speaker meaning — is inaccurate. In this line of thought, the paper pays a particular attention to hidden indexicals, anaphora and tense. The necessity of taking into account discursive parameters in order to solve semantic indeterminacy in such cases is argued for.