Flexibly Instructable Agents

This paper presents an approach to learning from situated, interactive tutorial instruction within an ongoing agent. Tutorial instruction is a flexible (and thus powerful) paradigm for teaching tasks because it allows an instructor to communicate whatever types of knowledge an agent might need in whatever situations might arise. To support this flexibility, however, the agent must be able to learn multiple kinds of knowledge from a broad range of instructional interactions. Our approach, called situated explanation, achieves such learning through a combination of analytic and inductive techniques. It combines a form of explanation-based learning that is situated for each instruction with a full suite of contextually guided responses to incomplete explanations. The approach is implemented in an agent called Instructo-Soar that learns hierarchies of new tasks and other domain knowledge from interactive natural language instructions. Instructo-Soar meets three key requirements of flexible instructability that distinguish it from previous systems: (1) it can take known or unknown commands at any instruction point; (2) it can handle instructions that apply to either its current situation or to a hypothetical situation specified in language (as in, for instance, conditional instructions); and (3) it can learn, from instructions, each class of knowledge it uses to perform tasks.Comment: See http://www.jair.org/ for any accompanying file

From Discursive Practice to Logic? Remarks on Logical Expressivism

This paper proposes a novel account of the conditional locution as grounded in practices of goal- directed cooperative dialogue. It is argued that a conditional semantics can be obtained within a language fragment that lacks this locution, but supports assertive, inferential and directive prac- tices. We take Brandom’s logical expressivist programme as a point of departure, but argue that this programme is empirically flawed as it underestimates the pervasive context-dependence of linguistic items including logical vocabulary. We further take issue with his claim that a discursive practice involving only assertion and inference is sufficient for the conservative introduction and deployment of conditional vocabulary. A more promising route is provided by the introduction of directives, as in so-called “pseudo-imperatives” such as Get individuals to invest their time and the funding will follow: this has a conditional sense that if individuals invest their time, then funding will follow. We propose a semantic analysis for these forms which builds on Kukla and Lance’s account of prescriptives, and argue that our analysis more faithfully captures the “irrealis” nature of conditionals. The analysis is presented in terms of an information-state based dialogue model, with the information state comprising a partitioned commitment store. It is argued that our “dialogical” analysis of conditional reasoning is faithful to Brandom’s Sellarsian intuition of linguistic practice as a game of giving and asking for reasons. We conclude by contextualising and situating Brandom’s programme against the larger field of practice theory, by means of a comparison with the works of sociologist, anthropologist and philosopher Pierre Bourdieu, and suggest that this com- parison reveals further challenges to the expressivist programme. We also take note of Narasimhan et al’s recent proposals for agent-based modelling of social practice theory as a possible basis for future development

Practical Language: Its Meaning and Use

I demonstrate that a "speech act" theory of meaning for imperatives is—contra a dominant position in philosophy and linguistics—theoretically desirable. A speech act-theoretic account of the meaning of an imperative !φ is characterized, broadly, by the following claims. LINGUISTIC MEANING AS USE !φ’s meaning is a matter of the speech act an utterance of it conventionally functions to express—what a speaker conventionally uses it to do (its conventional discourse function, CDF). IMPERATIVE USE AS PRACTICAL !φ's CDF is to express a practical (non-representational) state of mind—one concerning an agent's preferences and plans, rather than her beliefs. Opposed to speech act accounts is a preponderance of views which deny that a sentence's linguistic meaning is a matter of what speech act it is used to perform, or its CDF. On such accounts, meaning is, instead, a matter of "static" properties of the sentence—e.g., how it depicts the world as being (or, more neutrally, the properties of a model-theoretic object with which the semantic value of the sentence co-varies). On one version of a static account, an imperative 'shut the window!' might, for instance, depict the world as being such that the window must be shut. Static accounts are traditionally motivated against speech act-theoretic accounts by appeal to supposedly irremediable explanatory deficiencies in the latter. Whatever a static account loses in saying (prima facie counterintuitively) that an imperative conventionally represents, or expresses a picture of the world, is said to be offset by its ability to explain a variety of phenomena for which speech act-theoretic accounts are said to lack good explanations (even, in many cases, the bare ability to offer something that might meet basic criteria on what a good explanation should be like). I aim to turn the tables on static accounts. I do this by showing that speech act accounts are capable of giving explanations of phenomena which fans of static accounts have alleged them unable to give. Indeed, for a variety of absolutely fundamental phenomena having to do with the conventional meaning of imperatives (and other types of practical language), speech act accounts provide natural and theoretically satisfying explanations, where a representational account provides none