Paul E. Nielsen

Qualitative spatial reasoning: the CLOCK project

Spatial reasoning is ubiquitous in human problem solving. Significantly, many aspects of it appear to be qualitative. This paper describes a general framework for qualitative spatial reasoning and demonstrates how it can be used to understand complex mechanical systems, such as clocks. The framework is organized around three ideas. (1) We conjecture that no powerful, general-purpose, purely qualitative representation of spatial properties exists (the poverty conjecture). (2) We describe the MD/PV model of spatial reasoning, which overcomes this fundamental limitation by combining the power of diagrams with qualitative spatial representations. In particular, a metric diagram, which combines quantitative and symbolic information, is used as the foundation for constructing a place vocabulary, a symbolic representation of shape and space which supports qualitative spatial reasoning. (3) We claim that shape and connectivity are the central features of qualitative spatial representations for kinematics. We begin by exploring these ideas in detail, pointing out why simpler representations have not proven fruitful. We also describe how inferences can be organized using the MD/PV model. We demonstrate the utility of this model by describing clock, a program which reasons about complex two-dimensional mechanisms. clock starts with a CAD description of a mechanisms parts and constructs a qualitative simulation of how it can behave. clock successfully performed the first complete qualitative simulation of a mechanical clock from first principles, a milestone in qualitative physics. We also examine other work on qualitative spatial reasoning, and show how it fits into this framework. Finally, we discuss new research questions this framework raises.

Qualitative kinematics: a framework

Qualitative spatial reasoning has seen little progress This paper attempts to explain why We provide a framework for qualitative kinematics (QK), qualitative spatial reasoning about motion We propose that no general-purpose, purely qualitative kinematics exists. We propose instead the MD/PV model of spatial reasoning, which combines the power of diagrams with qualitative representations Next we propose connectivity as the organizing principle for kinematic state, and describe a set of basic inferences which every QK system must make. The frameworks utility is illustrated by considering two programs, one finished and one in progress We end by discussing the research questions this framework raises.

SOAR/IFOR: intelligent agents for air simulation and control

Producing realistic computer generated forces in a distributed integrated simulation requires flexible mission execution and behavior coordination within the agent itself as well as in its interactions with other agents. This paper focuses on the types of behavior required to produce a realistic airborne forward air controller in closely coordinated attack missions.

Real-time intelligent characters for a non-visual simulation environment

In recent years, there has been a fair amount of research directed toward the goal of developing virtual, human-like characters for simulation environments. Much of this work has focused on creating high-fidelity graphical animations that represent realistic human forms and movement. We are approaching the same goal from a different angle, focusing on the real-time generation of autonomous, intelligent behaviors that a virtual human must use to attain its goals in a complex environment. Because the emphasis of our work is on high-level behavior rather than visual representation, our current work is geared toward non-visual simulation environments. TacAir-Soar is a system that generates intelligent behavior for flying missions in simulated fixed-wing aircraft for military training simulations. The system has been in development for over five years, and has participated in multiple military training exercises. This paper presents many of the lessons we have learned in developing an autonomous, real-time system, together with suggestions for how these lessons might apply to the development of a full real-time, autonomous, virtual human that also incorporates realistic visual representation and movement.