Frameworks and Models in Engineering Systems
Engineering Systems Design (ESD.04J/1.041J)
Spring 2007
Models and Frameworks
DISPLAYS
SPEAKER: Joseph M. Sussman
MIT
April 3, 2007
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
Month YYYY].
Introduction to
Transportation Systems
Sussman, Joseph M., Artech House Publishers,
Boston and London, 2000.
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
Month YYYY].
2
Chapter 10:
Models and Frameworks
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
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Models and Frameworks:
An Introduction
‹ Models
are mathematical
representations of a system.
‹ Frameworks are qualitative
organizing principles for analyzing
a system.
‹ We can use both models and
frameworks to do analysis.
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
Month YYYY].
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What is our function as
transportation professionals?
‹ Designing
better transportation
systems
‹ Using resources, financial and
otherwise, effectively in a
transportation context
‹ Operating transportation systems
optimally
‹ Maintaining transportation systems
efficiently
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
Month YYYY].
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Value-laden words:
‹ better
‹ effectively
‹ optimally
‹ efficiently
These depend on your point of view.
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
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A Structure for Transportation
System Analysis
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
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A Systems Analysis Framework:
A First Look
1
Search for
alternatives in the
real world
Prediction of
performance,
flows, etc.
Evaluation of
alternatives
Figure 10.1
Reconsider
measures of
effectiveness
Selection among
alternatives
2
LOOP 1: Does the evaluation suggest other alternatives?
LOOP 2: Are the measures of effectiveness appropriate?
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
Month YYYY].
8
The Subtlety in Choosing
Measures of Effectiveness
Be sure your measures of effectiveness
are good
An Urban Area
High Income
Area
Low Income
Area
I
Figure 10.2
II
Center
City
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
Month YYYY].
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A Systems Analysis Framework:
A Second Look
Search for
alternatives in the
real world
1
3
Abstraction of real
world into
model / framework
Prediction of
performance,
flows, etc.
Evaluation of
alternatives
Reconsider
measures of
effectiveness
Selection among
alternatives
2
Figure 10.3
LOOP 1: Does the evaluation suggest other alternatives?
LOOP 2: Are the measures of effectiveness appropriate?
LOOP 3: Is the “abstraction” good at predicting?
We need to ask, “Is the abstraction any good?”
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
Month YYYY].
10
A Systems Analysis Framework:
A Third Look
Search for
alternatives in the
real world
1
3
Abstraction of real
world into
model / framework
Prediction of
performance,
flows, etc.
Insight:
Better understanding
of system behavior
Evaluation of
alternatives
Figure 10.4
Reconsider
measures of
effectiveness
Selection among
alternatives
2
LOOP 1: Does the evaluation suggest other alternatives?
LOOP 2: Are the measures of effectiveness appropriate?
LOOP 3: Is the “abstraction” good at predicting?
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
Month YYYY].
11
Why Are We Modeling?
‹
‹
‹
‹
Choosing the Best Alternative -Optimization
System Operation
Learn from Model Building Processes
Insight
“We may gain insight into complex
situations by first understanding simpler
situations resembling them.”
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
Month YYYY].
12
Modeling for Negotiation
‹
‹
Prodyut Dutt, in “A Standards-Based
Methodology for Urban Transportation Planning
in Developing Countries”, focused on how
planners work in developing countries versus
the way urban planners work in the developed
world. The essence of his research looked at
the differences in planning methodologies
necessary in the two environments.
Dutt developed “models for negotiation” -- the
idea of transparent models, where rather than
shielding the outside world from what was going
on within that “black box” model, planners could
look into the model and clearly see the
assumptions driving the trade-off about location
of corridors in urban areas.
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
Month YYYY].
13
The Model Is a Shaper of
Your World View
‹A
hammer is a fine tool, but it is not
very good for washing windows.
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
Month YYYY].
14
Modeling Approaches
‹
‹
‹
‹
‹
‹
‹
‹
‹
‹
‹
Network Analysis
Linear Programming
Non-linear Programming
Simulation
Deterministic Queuing
Probabilistic Queuing
Regression
Neural Networks
Genetic Algorithms
Cost/Benefit Analysis
Life-cycle Costing
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
Month YYYY].
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Modeling Approaches (continued)
‹
‹
‹
‹
‹
‹
‹
‹
‹
System Dynamics
Control Theory
Difference Equations
Differential Equations
Probabilistic Risk Assessment
Supply/Demand/Equilibrium
Game Theory
Statistical Decision Theory
Markov Models
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
Month YYYY].
16
Getting Answers from Models
Developing a model -- an abstraction -- and
getting results from it are two different things.
Search for
alternatives in the
real world
1
Abstraction of real
world into
model / framework
3
4
Can the model be
“solved” -- i.e.,
produce results?
Prediction of
performance,
flows, etc.
Insight:
Better understanding
of system behavior
Evaluation of
alternatives
Selection among
alternatives
Figure 10.5
LOOP 1:
LOOP 2:
LOOP 3:
LOOP 4:
Reconsider
measures of
effectiveness
2
Does the evaluation suggest other alternatives?
Are the measures of effectiveness appropriate?
Is the “abstraction” good at predicting?
Develop new abstraction.
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
Month YYYY].
17
Models vs. Frameworks
‹ Models
‹ Models
are a mathematical
representation of reality -quantitative in nature.
‹ Frameworks
‹ When
we talk about a framework,
we are generally talking about a
qualitative view of a complex
system. It is “a way of thinking” -a way of organizing our thinking
about a complex system.
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
Month YYYY].
18
Here is a framework we discussed earlier:
Joint Ownership/
Operation
Private Ownership/
Operation
Public Ownership/
Operation
Urban
Intercity
International
Traveler/
Pax
Freight
Figure 10.6
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
Month YYYY].
19
Simple vs. Complex Models
and Frameworks
MODEL
(Quantitative)
Useful
FRAMEWORK
(Qualitative)
Useful
SIMPLE
Not Useful
Useful
Not Useful
Useful
COMPLEX
Not Useful
Not Useful
Figure 10.7
Cite as: Joseph Sussman, course materials for ESD.04J Frameworks and Models in Engineering Systems, Spring
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD
Month YYYY].
20