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Updating Discourse Context with Active Logic. John Gurney. Khemdut Purang. Don Perlis. June 1996.
In this paper we present our implementation of a system of active logic that processes natural language discourses. We focus on problems that involve presupposition and the associated well-known problems of the projection of presupposition. We discuss Heim's largely successful theory of presupposition and point out certain limitations. We then use these observations to build our discourse processor based on active logic. Our main contributions are the handling of problems that go beyond the scope of Heim's theory , especially discourses the involve cancellation of presupposition. Ongoing work suggests that conversational implicature and the cancellation of implicature can also be treated by our methods. Key words: presupposition, discourse, con text, accommodation, active logic, implicature. (Also cross-referenced as UMIACS-TR-96-62) University of Maryland Institute for Advanced Computer Studies, Dept. of Computer Science, Univ. of Maryland, Army Research Laboratory, Adelphi MD,
Defaults Denied. Michael Miller. Don Perlis. Khemdut Purang. June 1996.
We take a tour of various themes in default reasoning, examining new ideas as well as those of Brachman, Delgrande, Poole, and Schlechta. An underlying issue is that of stating that a potential default principle is not appropriate. We see this arise most dramatically as a problem in an attempt to formalize what are often loosely called "prototypes", although it also arises in other formal approaches to default reasoning. Some formalisms in the literature provide solutions but not without costs. We propose a formalism that appears to avoid these costs; it can be seen as a step toward a population-based set-theoretic modification of these approaches, that may ultimately provide a closer tie to recent work on statistical (quantitative) foundations of (qualitative) defaults([1]). Our analysis in particular indicates the need to resolve a conflation between use and mention in many default formalisms. Our treatment proposes such a resolution, and also explores the use of sets toward a more population-based notion of default. (Also cross-referenced as UMIACS-TR-96-61) University of Maryland Institute for Advanced Computer Studies, Dept. of Computer Science, Univ. of Maryland, Intelligent Automation Inc., Rockville MD,
Active Logic and Heim's Rules for Updating Discourse Context. John Gurney. Don Perlis. Khemdut Purang. June 1996.
Discourse unfolds in time, giving rise to a cascade of belief changes in the listener. Yet this temporal evolution of discourse and belief is typically ignored in theoretical treatments of discourse. It has been claimed (see Soames~\cite{soames:presuppositions}) that Heim's~\cite{heim:projection_problem} theory of discourse context accounts for non-implicative discourse updating. We will present a new non-implicative discourse that cannot be accounted for with Heim's use of global or local accommodation and which appears to require attention to \emph{evolution} of discourse. We use this example to motivate remaking Heim's update function, aimed toward a unified approach to discourse---one in which Heim's rules for discourse updating can account for more of the problem cases for the theory of discourse context. These rules and the revised update function can then serve as principles that constrain the building of representations for discourse context (such as the Discourse Representation Structures, of Discourse Representation Theory, ~\cite{kamp:reyle}). We propose \emph{active logic} as a convenient tool for executing the required inferences (as called for by our revised version of Heim's update function) as the discourse evolves through time. (Also cross-referenced as UMIACS-TR-96-43) University of Maryland Institute for Advanced Computer Studies, Dept. of Computer Science, Univ. of Maryland,
Active Logic Applied to Cancellation of Gricean Implicture. Khemdut Purang. Don Perlis. John Gurney. June 1996.
Dialog proceeds over time, during which inferred beliefs come and go in the listener. Yet this temporal aspect of dialog and belief is typically ignored in theoretical treatments of dialog. Using a simple example of a dialog with an implicature that arises partway through and then is later retracted, we discuss how Gricean maxims and nonmonotonicity may relate to each other and to a computational treatment of implicature. In effect we seek to track reasoning along Gricean lines over time. We present our own computational approach to this, giving an implementation in the formalism of active logics. (Also cross-referenced as UMIACS-TR-96-42) University of Maryland Institute for Advanced Computer Studies, Dept. of Computer Science, Univ. of Maryland,
Conversational Adequacy: Mistakes are the Essence. Don Perlis. Khemdut Purang. June 1996.
We argue that meta-dialog and meta-reasoning, far from being of only occasional use, are the very essence of conversation and communication between agents. We give four paradigm examples of massive use of meta-dialog where only limited base dialog may be present, and use these to bolster our claim of centrality for meta-dialog. We further illustrate this with related work in active logics. We argue moreover that there may be a core set of meta-dialog principles that is in some sense complete. If we are right, then implementing such a set would be of considerable interest. We give examples of existing computer programs that converse inadequately according to our guidelines. (Also cross-referenced as UMIACS-TR-96-41) University of Maryland Institute for Advanced Computer Studies, Dept. of Computer Science, Univ. of Maryland,
Don Perlis. July 1994.
An Error-Theory of Consciousness. I argue that consciousness is an aspect of an agent's intelligence, hence of its ability to deal adaptively with the world. In particular, it allows for the possibility of noting and correcting the agent's own errors. This in turn requires a robust self model as part of its world model, as well as the capability to come to see that world model as residing in its belief base (part of its self model), while then representing the actual world as possibly different, i.e., forming a new world model. This suggests particular computational mechanisms by which consciousness occurs, ones that conceivably could be discovered by neuroscientists, as well as built into artificial systems that may need such capabilities. Consciousness, then, would not be an epiphenomenon at all, but rather a key part of the functional architecture of suitably intelligent agents, hence amenable to study as much as any other architectural feature. (Also cross-referenced as UMIACS-TR-94-91) University of Maryland Institute for Advanced Computer Studies, Dept. of Computer Science, Univ. of Maryland,
Michael Miller. Don Perlis. May 1994.
What experts deny, novices must understand. We consider the problem of representing the denial of default information. We show that such denials are important parts of commonsense reasoning. Moreover, their representation is not a simple matter of negating traditional representations of default information. We have found a solution by separating default information into use and trend portions. This approach may also afford a more compact way to represent defaults in general. (Also cross-referenced as UMIACS-TR-94-64) University of Maryland Institute for Advanced Computer Studies, Dept. of Computer Science, Univ. of Maryland,
Jennifer Elgot-Drapkin. Diana Gordon. Sarit Kraus. Michael Miller. Madhura Nirkhe. Don Perlis. May 1994.
Calibrating, Counting, Grounding, Grouping. Even an ``elementary'' intelligence for control of the physical world will require very many kinds of knowledge and ability. Among these are ones related to perception, action, and reasoning about ``near space'': that region comprising one's body and the portion of space within reach of one's effectors; chief among these are individuation and categorization of objects. These in turn are made useful in part by the additional capacities to estimate category size, change one's beliefs about categories, and form new categories or revise old categories. In this position paper we point out some issues in knowledge representation that can arise with respect to the above capacities, and suggest that the framework of ``active logics'' (see below) may be marshaled toward solutions. We will conduct our discussion in terms of learning to understand in a semantically explicit way one's own sensori-motor system and its interactions with near-space objects. (Also cross-referenced as UMIACS-TR-94-63) University of Maryland Institute for Advanced Computer Studies, Dept. of Computer Science, Univ. of Maryland,
Don Perlis. May 1994.
Logic for a lifetime. There has been an explosion of formal work in commonsense reasoning in the past fifteen years, but almost no significant connection with work in building commonsense reasoning systems (cognitive or otherwise). We explore the reasons, and especially the ideal formal assumption of omniscience, reviewing and extending arguments that this is irreparably out of line with the needs of any real reasoning agent. On the other hand, this exploration reveals some desiderata that might still be given useful formal treatment, but with a somewhat altered set of aims from what has motivated most formal work. The discussion is motivated by several examples of commonsense reasoning, involving change of belief in addition to the more usual arguments concerning resource limitations. Key to the entire discussion is the notion that real reasoners do not usually have the luxury of isolated problems with well-defined beginnings and endings, but rather must deal with evolving and ongoing problems and situations. (Also cross-referenced as UMIACS-TR-94-62) University of Maryland Institute for Advanced Computer Studies, Dept. of Computer Science, Univ. of Maryland,
Madhura Nirkhe. Sarit Kraus. Don Perlis. March 1994.
Thinking takes time: a modal active-logic for reasoning in time. Most common sense reasoning formalisms do not account for the passage of time a s the reasoning occurs, and hence are inadequate from the point of view of modeling an agent's {\em ongoing} process of reasoning. We present a modal active-logic that treats time as a valuable resource that is consumed in each step of the agent's reasoning. We provide a sound and complete characterization for this logic and examine how it addresses the problem of logical omniscience. (Also cross-referenced as UMIACS-TR-94-39) University of Maryland Institute for Advanced Computer Studies, Dept. of Computer Science, Univ. of Maryland,
Michael Miller. Don Perlis. March 1994.
Presentations and this and that: logic in action. The tie between linguistic entities (e.g., words) and their meanings (e.g., objects in the world) is one that a reasoning agent had better know about and be able to alter when occasion demands. This has a number of important commonsense uses. The formal point, though, is that a new treatment is called for so that rational behavior via a logic can measure up to the constraint that it be able to change usage, employ new words, change meanings of old words, and so on. Here we do not offer a new logic per se; rather we borrow an existing one (step logic) and apply it to the specific issue of language change. (Also cross-referenced as UMIACS-TR-94-36) University of Maryland Institute for Advanced Computer Studies, Dept. of Computer Science, Univ. of Maryland,
Don Perlis. March 18, 1994.
Consciousness and complexity: the cognitive quest. March 1994.
Some implications of the view that mind is a suitably complex kind of process are investigated in various contexts. The underlying theme is that the behavior of complex systems cannot be adequately judged by that of simple systems. I first present a personal exploration of the mechanistic account of mind in terms of non-technical considerations; then I present and criticize some ideas of Kripke, Nagel, and Jackson that challenge the mechanistic view. Next I turn to a brief synopsis of some of Dennett's recent ideas. Finally I offer some critical comments on Dennett's views and suggest possible modifications. (Also cross-referenced as UMIACS-TR-94-25) University of Maryland Institute for Advanced Computer Studies, Dept. of Computer Science, Univ. of Maryland,
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