Showing papers by "Paul Morris published in 2000"

Planning in interplanetary space: theory and practice

Abstract: On May 17th 1999, NASA activated for the first time an AI-based planner/scheduler running on the flight processor of a spacecraft. This was part of the Remote Agent Experiment (RAX), a demonstration of closed-loop planning and execution, and model-based state inference and failure recovery. This paper describes the RAX Planner/Scheduler (RAX-PS), both in terms of the underlying planning framework and in terms of the fielded planner. RAX-PS plans are networks of constraints, built incrementally by consulting a model of the dynamics of the spacecraft. The RAX-PS planning procedure is formally well defined and can be proved to be complete. RAX-PS generates plans that are temporally flexible, allowing the execution system to adjust to actual plan execution conditions without breaking the plan. The practical aspect, developing a mission critical application, required paying attention to important engineering issues such as the design of methods for programmable search control, knowledge acquisition and planner validation. The result was a system capable of building concurrent plans with over a hundred tasks within the performance requirements of operational, mission-critical software.

Execution of Temporal Plans with Uncertainty

Abstract: Simple Temporal Networks (STNs) have proved useful in applications that involve metric time However, many applications involve events whose timing is uncertain in the sense that it is not controlled by the execution agent In this paper we consider execution algorithms for temporal networks that include events of uncertain timing We present two such algorithms The first retains maximum flexibility, but requires potentially costly updates during execution The second surrenders some flexibility in order to obtain a fast execution comparable to that available for ordinary STNs

Beyond Anecdotes: An Empirical Study of "Anthropomorphism"

Abstract: The status of "anthropomorphic" descriptions of animals in terms of intentions and emotions has been generally regarded as a prescriptive methodological concern. In contrast, in the study of human social psychology the nature of psychological descriptions of other people has been approached as a substantive empirical issue. Following this lead, the present study investigated the nature of people's descriptions of short videotaped episodes of animal behavior. The descriptions obtained were predominantly anthropomorphic and structured according to a limited set of "event units" whose psychological meaning was highly consistent across the observers. In common with many social psychologists we conclude that consistency of anthropomorphic description suggests that meaning is specified within the structure of behavior.

On Reformulating Planning as Dynamic Constraint Satisfaction

Abstract: In recent years, researchers have reformulated STRIPS planning problems as SAT problems or CSPs. In this paper, we discuss the Constraint-Based Interval Planning (CBIP) paradigm, which can represent planning problems incorporating interval time and resources. We describe how to reformulate mutual exclusion constraints for a CBIP-based system, the Extendible Uniform Remote Operations Planner Architecture (EUROPA). We show that reformulations involving dynamic variable domains restrict the algorithms which can be used to solve the resulting DCSP. We present an alternative formulation which does not employ dynamic domains, and describe the relative merits of the different reformulations.