Browsing by Author "Kraus, Sarit"
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Item Active Logics: A Unified Formal Approach to Episodic Reasoning(1999-10-14) Elgot-Drapkin, Jennifer; Kraus, Sarit; Miller, Michael; Nirkhe, Madhura; Perlis, DonaldArtificial intelligence research falls roughly into two categories: formal and implementational. This division is not completely firm: there are implementational studies based on (formal or informal) theories (e.g., CYC, SOAR, OSCAR), and there are theories framed with an eye toward implementability (e.g., predicate circumscription). Nevertheless, formal/theoretical work tends to focus on very narrow problems (and even on very special cases of very narrow problems) while trying to get them ``right'' in a very strict sense, while implementational work tends to aim at fairly broad ranges of behavior but often at the expense of any kind of overall conceptually unifying framework that informs understanding. It is sometimes urged that this gap is intrinsic to the topic: intelligence is not a unitary thing for which there will be a unifying theory, but rather a ``society'' of subintelligences whose overall behavior cannot be reduced to useful characterizing and predictive principles. Here we describe a formal architecture that is more closely tied to implementational constraints than is usual for formalisms, and which has been used to solve a number of commonsense problems in a unified manner. In particular, we address the issue of formal, integrated, and longitudinal reasoning: inferentially-modeled behavior that incorporates a fairly wide variety of types of commonsense reasoning within the context of a single extended episode of activity requiring keeping track of ongoing progress, and altering plans and beliefs accordingly. Instead of aiming at optimal solutions to isolated, well-specified and temporally narrow problems, we focus on satisficing solutions to under-specified and temporally-extended problems, much closer to real-world needs. We believe that such a focus is required for AI to arrive at truly intelligent mechanisms with the ability to behave effectively over considerably longer time periods and range of circumstances than is common in AI today. While this will surely lead to less elegant formalisms, it also surely is requisite if AI is to get fully out of the blocks-world and into the real world. (Also cross-referenced as UMIACS-TR-99-65)Item Calibrating, Counting, Grounding, Grouping(1998-10-15) Elgot-Drapkin, Jennifer; Gordon, Diana; Kraus, Sarit; Miller, Michael; Nirkhe, Madhura; Perlis, DonEven 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)Item Contracting Tasks in Multi-Agent Environments(1998-10-15) Kraus, SaritAgents may contract some of their tasks to other agent even when they do not share a common goal. An agent may try to contract some of the tasks that it cannot perform by itself, or that may be performed more efficiently by other agents. One self-motivated agent may convince another self-motivated agent to help it with its task, by promises of rewards, even if the agents are not assumed to be benevolent. We propose techniques that provide efficient ways to reach contracting in varied situations: the agents have full information about the environment and each other or subcontracting when the agents do not know the exact state of the world. We consider situations of repeated encounters, cases of asymmetric information, situations where the agents lack information about each other, and cases where an agent subcontracts a task to a group of agents. Situations where there is competition among possible contracted agents or possible contracting agents are also considered. In all situations we would like the contracted agent to carry out the task efficiently without the need of close supervision by the contracting agent. (Also cross-referenced as UMIACS-TR-94-44)Item Representing and Integrating Multiple Calendars(1998-10-15) Kraus, Sarit; Sagiv, Yehoshua; Subrahmanian, V. S.Whenever humans refer to time, they do so with respect to a specific underlying calendar. So do most software applications. However, most theoretical models of time refer to time with respect to the integers (or reals). Thus, there is a mismatch between the theory and the application of temporal reasoning. To lessen this gap, we propose a formal, theoretical definition of a calendar and show how one may specify dates, time points, time intervals, as well as sets of time points, in terms of constraints with respect to a given calendar. Furthermore, when multiple applications using different calendars wish to work together, there is a need to integrate those calendars together into a single, unified calendar. We show how this can be done. (Also cross-referenced as UMIACS-TR-97-12)Item Secure Agents(1999-10-07) Bonatti, Piero; Kraus, Sarit; Subrahmanian, V. S.With the rapid proliferation of software agents, there comes an increased need for agents to ensure that they do not provide data and/or services to unauthorized users. We first develop an abstract definition of what it means for an agent to preserve data/action security. Most often, this requires an agent to have knowledge that is impossible to acquire --- hence, we then develop approximate security checks that take into account, the fact that an agent usually has incomplete/approximate beliefs about other agents. We develop two types of security checks --- static ones that can be checked prior to deploying the agent, and dynamic ones that are executed at run time. We prove that a number of these problems are undecidable, but under certain conditions, they are decidable and (our definition of) security can be guaranteed. Finally, we propose a language within which the developer of an agent can specify her security needs, and present provably correct algorithms for static/dynamic security verification. (Also cross-refernced as UMIACS-TR-99-62)Item Thinking takes time: a modal active-logic for reasoning in time(1998-10-15) Nirkhe, Madhura; Kraus, Sarit; Perlis, DonMost 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)