Tim@UPENN.CSNET (Tim Finin) (02/17/86)
From: Tim Finin <Tim%upenn.csnet@CSNET-RELAY.ARPA>
Forwarded From: Paul Fishwick <Fishwick@UPenn> on Sun 16 Feb 1986 at 12:54
HIERARCHICAL REASONING:
SIMULATING COMPLEX PROCESSES
OVER MULTIPLE LEVELS OF ABSTRACTION
Paul A. Fishwick
University of Pennsylvania
Ph.D. Defense
This talk describes a method for simulating processes over multiple levels of
abstraction. There has been recent work with respect to data, object, and
problem-solving abstraction, however, abstraction in simulation has not been
adequately explored. We define a process as a hierarchy of distinct production
rule sets that interface to each other so that abstraction levels may be
bridged where desired. In this way, the process may be studied at abstraction
levels that are appropriate for the specific task: notions of qualitative and
quantitative reasoning are integrated to form a complete process description.
The advantages to such a description are increased control, computational
efficiency and selective reporting of simulation results. Within the framework
of hierarchical reasoning, we will concentrate on presenting the primary
concept of process abstraction.
A Common Lisp implementation of the hierarchical reasoning theory called HIRES
is presented. HIRES allows the user to reason in a hierarchical fashion by
relating certain facets of the simulation to levels of abstraction specified in
terms of actions, objects, reports, and time. The user is free to reason about
a process over multiple levels by weaving through the levels either manually or
via automatically controlled specifications. Capabilities exist in HIRES to
facilitate the creation of graph-based abstraction levels. For instance, the
analyst can create continuous system models (CSMP), petri net models, scripts,
or generic graph models that define the process model at a given level. We
present a four-level elevator system and a two-level "dining philosophers"
simulation. The dining philosophers simulation includes a 3-D animation of
human body models.
Time: Wednesday, February 26, 3pm
Place: Moore School, Room 554
Committee:
Dr. Norman Badler (Adviser)
Dr. Timothy Finin (Chairman)
Dr. Insup Lee
Dr. Richard Paul