Goals and Actions in Natural Language Instructions

Human agents are extremely flexible in dealing with Natural Language instructions: they are able both to adapt the plan they are developing to the input instructions, and vice versa, to adapt the input instructions to the plan they are developing. Borrowing the term from [Lewis 1979], I call this two-way adaptation process accommodation. In this proposal, I first define accommodation in the context of processing instructions. I then provide evidence for the particular inferences I advocate, and for the further claim that such inferences are directed by the goal to achieve which certain action is performed. The evidence I provide comes from my analysis of naturally occurring instructions, and in particular of purpose clauses and of negative imperatives. Finally, I propose a computational model of instructions able to support accommodation inferences. Such model is composed of: a speaker / hearer model of imperatives, based on the one presented in [Cohen and Levesque 90]; an action representation formalism based on a hybrid system, á la KRYPTON [Brachman et al. 1983a], whose primitives are those proposed in [Jackendoff 1990]; and inference mechanisms that contribute to building the structure of the intentions that the agent develops while interpreting instructions

Learning Features that Predict Cue Usage

Our goal is to identify the features that predict the occurrence and placement of discourse cues in tutorial explanations in order to aid in the automatic generation of explanations. Previous attempts to devise rules for text generation were based on intuition or small numbers of constructed examples. We apply a machine learning program, C4.5, to induce decision trees for cue occurrence and placement from a corpus of data coded for a variety of features previously thought to affect cue usage. Our experiments enable us to identify the features with most predictive power, and show that machine learning can be used to induce decision trees useful for text generation.Comment: 10 pages, 2 Postscript figures, uses aclap.sty, psfig.te

Reconstructed Intentions in Collaborative Problem Solving Dialogues

We provide evidence that speech act recognition, is 1) difficult for humans to do and 2) likely to misidentify proposals involving reconstructed intentions. We examine the reliability of coding for speech acts in collaborative dialogues and we present an approach for recognizing reconstructed proposals using domain context and other more easily recognized features. 1 Introduction Speech act recognition plays a prominent role in dialogue understanding, in traditional approaches that infer a plan using plan construction operators [PA80], [LA90], [LC91, LC92], and in more recent techniques relying on statistical correlations or finite state machines [RM95, QDL + 97]. Both approaches recognize surface speech acts, using surface form and information provided by the discourse context and the discourse operators, or by a finite state approximation of the planning information. These approaches assume that it is (relatively) simple to recognize speech acts, and that speech acts are a requi..

The world-sheet description of A and B branes revisited

We give a manifest supersymmetric description of A and B branes on Kahler manifolds using a completely local N=2 superspace formulation of the world-sheet nonlinear sigma-model in the presence of a boundary. In particular, we show that an N=2 superspace description of type A boundaries is possible, at least when the background is Kahler. This leads to an elegant and concrete setting for studying coisotropic A branes. Here, apgesan important role is played by the boundary potential, whose precise physical meaning remains to be fully understood. Duality transformations relating A and B branes in the presence of isometries are studied as well.Comment: LaTeX, 32 page

A Thermodynamic Interpretation of Time for Superstring Rolling Tachyons

Rolling tachyon backgrounds, arising from open strings on unstable branes in bosonic string theory, can be related to a simple statistical mechanical model - Coulomb gas of point charges in two dimensions confined to a circle, the Dyson gas. In this letter we describe a statistical system that is dual to non-BPS branes in superstring theory. We argue that even though the concept of time is absent in the statistical dual sitting at equilibrium, the notion of time can emerge at the large number of particles $N \to \infty$ limit.Comment: 6 pages, 3 figures, v2: reference added, v3: minor clarification, version to appear in journa