PACT and RAPID: Multi-Agent
Design and Concurrent
Engineering
by Greg Milette
CS525M, Spring 2002
The Plan
•Describe the problem.
•Describe how PACT solves the problem.
•Describe how RAPPID solves the problem.
(23 slides)
Concurrent Engineering
The Problem
•Each engineering group is specialized but must
coordinate designs.
•Different engineering groups use their own
specialized design tools.
•Each with different assumptions, conventions, and limitations.
•Different tools are highly specialized and cannot be
to converted.
Solutions
•Allow groups to use their own specialized tools,
while enabling the groups to reason collectively
about design.
PACT is
-A system designed to integrate existing multi-tool systems.
-Uses agent communication and common ontology.
RAPPID is
-A system design to reason about trade-offs.
-Using market dynamics and set-based reasoning.
PACT: The Agents for the Design
of a Manipulator
Sharing design models
A) could be hard to scale
B) scales well but requires:
•Way to coordinate interactions (Facilitators)
•Way to express design decisions (Agent
Messages)
Advantage of Sharing Design
Model
•A unified model is not needed. Instead tool models are
encapsulated.
•Shared engineering language is needed for communication.
It only has to cover a the shared design model
•Communication is formally defined, through KIF and
KQML, which increases modularity.
Facilitators
•The four specific functions a facilitator provides:
•Translates tool-specific knowledge into and out of
standard knowledge exchange language.
•Provides a layer of reliable message passing.
•Routs outgoing messages to appropriate destination.
•Initializes and monitors the execution.
Shared Model
Agent’s Model
Facilitator
Agent
Ontology
•Was needed to express engineering concepts.
•Example concept: voltage on a wire.
•What units?
•What time interval discrete or continuous?
•Better to agree on a method for describing
information. Do not standardize.
Example sentences using ontology:
(physical-dimension length)
(unit-of-measure inch)
(quantity (diameter shaft-a)) (= (diameter shaft-a)
How to Develop an Ontology
•Developers met and role-played how their
components would respond
•Then corresponded by email.
•But this would not work in a larger project, which
need standard ontologies.
Example of Distributed ReDesign
Assert part
number
#1234.
Dimensions
3.0 x 3.0
meters.
Digital
Circuitry +
component catalog
Control
Adjust design
Assert part
number #1234.
Dimensions
?x.
Mechanism
Power System
and Sensors
Assert new motor
part # 1234
PACT
•Model – each agent models the world in it’s own way, it will
communicate its model through a shared language.
•Agent structure:
•Each agent can be in a different physical location.
•Federation architecture through facilitators.
•Communication – KQML, KIF, TCP/IP and email messaging
•Ontology – allows engineering concepts to be transferred
What is RAPPID?
•Agents can reason about the trade-offs
among design options using set-based
reasoning.
•Example of trade-off: How much power should
be budgeted for sensor circuitry? And the
actuator?
•Can solve a big optimization problem
•Consider many design alternatives
automatically.
Two types of agents
•Components –
•Represents a part of the design.
•Buys and sells characteristics in the market.
•Might be organized in a hierarchy.
•Might be controlled by a human user.
•Characteristics –
•Definable attribute like weight or power.
•Maintains a marketplace for that item.
The RAPPID System
What is Set-Based Reasoning?
http://www.erim.org/cec/rappid/rappid.htm
Set-Based Reasoning in Context
•Low prices = slack characteristics
•High prices = constrained characteristics
•Space can be collapsed by buying up allocations of
characteristics…
•Which gives other agents more funds to purchase other
characteristics instead…
•Which causes the amount of certain characteristics to get
fewer and converge on a price.
Set-Based Reasoning
Reasoning About Bids
Conclusions
•In concurrent engineering groups:
•Are isolated because they use different techniques and
models to solve problems.
•But they need to reason collectively.
•PACT: Use communication and a shared ontology to
exchange design decisions.
•RAPPID: Use market dynamics and set-based reasoning so
agents can reason about the trade-offs of design choices.
References
•M. R. Cutkosky, R. S. Englemore, R. E. Fikes, T. R. Gruber, M. R. Genesereth,
W. S. Mark, J. M. Tenenbaum, and J. C. Weber. PACT: An Experiment in
Integrating Concurrent Engineering Systems. IEEE Computer, 26
(Januarty)(1):28-37,1993
•H. V. D. Parunak. RAPPID Project Index Page.
http://www.erim.org/cec/rappid/rappid.htm, 2002
•Weiss, Gerhard(Ed.), Parunak, H Van Dyke "Multiagent Systems: A Modern Approach
to Distributed Artificial Intelligence.", MIT Press, p378-416, 1999. ISBN
•Kuokka et all, “SHADE: Knowledge-Based Technology for the Re-Engineering
Problem”, http://www.ksl.stanford.edu/knowledge-sharing/papers/shadeoverview.html, 2002
•Parsons et all., “A Hybrid Agent Approach for Set-Based Conceptual Ship
Design,” http://www.erim.org/cec/rappid/rappid.htm, 2002
The End