Transcript Slide 1

Presented to: Center for Sceince and Math Education
University of Texas, Austin, April 2009.
DEVS-Centered Modeling and Simulation:
Core Concepts for Engineering Education
Bernard P. Zeigler
Arizona Center for Integrative Modeling and Simulation
University of Arizona, Tucson
and
RTSync Corporation
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Outline and Claims
• Intro to Discrete Event Systems Specification (DEVS)
• Why it is a good basis for generic, domain independent
education in modeling and simulation
• How can we foster such generic abstraction-based concepts
while providing concrete tool-based experience?
• Inherent hurdles can be overcome with appropriate concept
sequencing and user-friendly feedback tools
• Can we learn from recent video game trends?
• Recent DEVS-based environments provide some clues
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Background: DEVS M&S Framework
Discrete Event Systems Specification (DEVS)
• Based on mathematical formalism using
system theoretic principles
• Separation of Model, Simulator and
Experimental Frame
• Atomic and Coupled types
• Hierarchical modular composition
Experimental Frame
Level Name
System Specification at this level
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Coupled
Systems
I/O System
Structure
I/O
Function
System built from component systems with coupling
recipe.
System with state and state transitions to generate the
behavior.
Collection of input/output pairs constituting the allowed
behavior partitioned according to initial state of the
system. The collection of I/O functions is infinite in
principle because typically, there are numerous states to
start from and the inputs can be extended indefinitely.
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I/O
Behavior
Collection of input/output pairs constituting the allowed
behavior of the system from an external Black Box view.
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I/O Frame Input and output variables and ports together with
allowed values.
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2
Source
Simulator
System
Modeling
Relation
Model
Simulation
Relation
message
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Scuba Diver Example
Level
Name
System Specification at this
level
System built from component
systems with coupling recipe.
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Coupled
Systems
3
I/O System
Structure
2
I/O Function
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I/O Behavior
Collection of input/output pairs Diver’s outputs under the surface over time in
response to external inputs
constituting the allowed
behavior of the system from an
external Black Box view.
0
I/O Frame
Input and output variables and Diver’s receivable signals (inputs) and generatable
signals (output)
ports together with allowed
values.
System consisting of diver, diver’s air supply, dive
boat, and water environment
Diver’s decision algorithm to execute planned dive
System with state and state
transitions to generate the
behavior.
Collection of input/output pairs Diver’s planned dive trajectory – levels and time at
each level starting on surface
constituting the allowed
behavior partitioned according
to initial state of the system.
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Some Types of Models
Represented in DEVS
Atomic Models
Ordinary
Differential
Equation
Models
Processing/
Queuing/
Coordinating
Spiking
Neuron
Models
can be
components
in a coupled
model
Petri Net
Models
Networks,
Collaborations
Processing
Networks
Discrete
Time/
StateChart
Models
Stochastic
Models
Fuzzy Logic
Models
Coupled Models
Partial
Differential
Equations
Physical
Space
Spiking
Neuron
Networks
n-Dim
Cell Space
Cellular
Automata
Quantized
Integrator
Models
Reactive
Agent
Models
Multi
Agent
Systems
Self Organized
Criticality
Models
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Co-Model Development Methodology*
Recognizes Domain, M&S, and Computational Engineers
Collaborative Development
* Tag Gon Kim, “Co-modeling method for the development of domain-specific models”, DEVS Symposium,
SpringSim, 2009
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Sequencing the Introduction to DEVS with Finite DEVS
•
•
•
•
Finite DEVS : Atomic models
– Ports: input, output
– States, including starting state
– Functions: time advance, internal transition, external transition, output
Behavior of Finite DEVS
– Injecting inputs
– Observing state transitions, outputs
Compositions of Finite DEVS
– Coupled models via automated port-matching coupling
Behavior of Coupled Models:
– Message exchange
– State trajectory
– Output trajectory
Can we develop student-friendly feedback tools that support progress from
step to step?
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Interactive Tutorials –
Define DEVS models within a restricted class
Traffic Light Control System
http://www.cs.gsu.edu/DEVSTutorial/
DevsTut
orial
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DEVS Tracking – Selectable Visual Display in Real Time
http://acims1.eas.asu.edu/WebStarts/
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Systems Problem Types
Systems Problem
systems analysis
systems design
systems inference
systems diagnosis
Does source of the data exist? What
are we trying to learn about it?
The system being analyzed may exist
or may be planned. In either case we
are trying to understand its behavioral
characteristics.
The system being designed does not yet
exist in the form that is being
contemplated. We are trying to come
up with a good design for it.
Which level transition is
involved?
moving from higher to lower
levels, e.g., using simulation to
generate a model’s behavior
moving from lower to higher
levels, e.g. having a means to
generate observed data,
synthesizing it with components
taken off the shelf.
The system exists. We are trying to
moving from lower to higher
infer how it works from observations of levels, e.g., having data, finding a
its behavior.
means to generate it
The system exists but is not behaving moving from errant behavior to the
correctly. We are trying to infer what possible causes as departures from
is wrong by observations of its
the correct structure
responses to selected inputs or
structure changes
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More radical approaches: Figuring out the Video Game
• Recent games are challenging players to figure out
what the rules are, rather then developing the skill
• Serious games seek to teach traditional subjects
• Can we learn from these trends to develop
educational technology?
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Incidental Learning in trying to figure out how it works
and why it is not working
•
Different from
– debugging in that the system was not of your making
– diagnosing in that there are no prescribed inference patterns to follow
•
Try something and see what happens
– Continue experimenting until exhausted or convinced that you need some help
•
Consult with others
– Go to the knowledge base web site
– Google to see if prior issue like this has been discussed
•
Read the manual – as a last resort – it has too much that is irrelevant to
immediate concern
The result is knowledge about the system that is not of the classical
lecture or book study variety
Can we foster this kind of “learning by experimenting” in a more
deliberate way?
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But what kind of knowledge could this be?
• Surface knowledge
–
–
–
–
Rule-based/ condition/action
Procedural/ how to knowledge
case based reasoning
does not go far beyond the base, like knowing only a few routes though a
city
– so can’t take alternative routes, can’t get outside familiar limits
• Deep knowledge
–
–
–
–
integrative
Understands global structures and relationships
can go beyond the base, like having put together a conceptual map of a city,
so can take detours, navigate in general directions
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Fostering “learning by experimenting”
or “active learning”
• Objective: foster acquisition of deep knowledge about
systems and models
• Use the conceptual framework of systems concepts and
M&S
• Provide computer environment and software tool set that
–
–
–
–
illustrates abstract concepts in concrete terms
make it easy to experiment
provide rich visualization
provide extensive feedback
• Encourage experimentation through incentive structures
that reward learning from mistakes (without overly
encouraging mistakes)
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Automating Test Frame Development
Legend:
DEVSJAVA
implementation
FDDEVS
specification
TEST
Frame
Specification
=
automated
DEVSJAVA
implementation
TEST
Frame
Implementation
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Automating Test Frame Feedback to a student experimenter
Student can
edit the
original
FDDEVS
specification
DEVSJAVA
implementation
DEVSJAVA
implementation
TEST
Frame
Implementation
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The test frame
remains the
same
The test frame
reports differences
in the behavior
resulting from
student's edits
Text is displayed in progressive
order with state related lines
grouped together for easier
understanding
FDDEVS
Summary
• DEVS-based instruction provides a generic, domain
independent approach to education in modeling and
simulation
• The inherent hurdles can be overcome with appropriate
concept sequencing and user-friendly feedback tools
• The major benefits include:
– ability to understand systems and develop transdisciplinary models
– provide M&S support for Systems (and systems of systems) engineering
approaches
– openness to creative approaches to highly complex problems
• Can we foster video game “learning by experimenting” in a
more deliberate way?
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Books and Web Links
devsworld.org
www.acims.arizona.edu
Rtsync.com
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More Demos and Links
http://www.acims.arizona.edu/demos/demos.shtml
• NTAC_DEMO (Marketplace_demo, MarketplaceObserver_demo)
• Integrated Development and Testing Methodology:
• AutoDEVS (ppt) & DEMO
– Natural language-based Automated DEVS model generation
– BPMN/BPEL-based Automated DEVS model generation
– Net-centric SOA Execution of DEVS models
– DEVS Unified Process for Integrated Development and Testing of SOA
•
Intrusion Detection System on DEVS/SOA
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