The Mythical Man-Month
Due Today: Code & Coding Standards
Due Next Class: Quiz #3; see webpage
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Mythical Man-Month I
Bio Break
Mythical Man-Month II
Questions / Review for Quiz #3
Chapter 1: Key Points
• Program = Useful to the programmer in the garage
• Programming Product = Useful to anyone
• Programming System Component = Part of a collection of programs
that work together doing a bigger job
• Programming Systems Product = The collection of components; what
you are after, 9X as expensive as creating a “program”
Program
3x
Programming
System
3x
Programming
Product
Programming
Systems
Product
Chapter 2: Key Points
• “All programmers are optimists”
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“Men and months are interchangeable commodities only when a task can be
partitioned among many workers with no communication between them.”
“The bearing of a child takes nine months, no matter how many women are
assigned.”
Costs: training. Intercommunication.
“Take no small slips” (in schedule)
Brooks Law: “Adding manpower to a late software project makes it later.”
– Abdel-Hamid & Madnick 1991: “Adding more people to a late project always
makes it more costly, but does not always cause it to be completed later.” 
Perhaps: Brook’s “rule of thumb.”
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Bottom line: Non-linear trade-off between persons and person-months
Perfectly Partitionable
Perfectly Partitionable Task
120
100
months
80
60
40
20
0
1
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4
5
6
people
7
8
9
10
Not Partitionable
Unpartitionable Task
120
100
months
80
60
40
20
0
1
2
3
4
5
6
people
7
8
9
10
Add Communication Costs
Partitionable w/ communication
120
100
Months
80
60
40
20
0
1
2
3
4
5
6
people
7
8
9
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Complex Inter-relationships
Complex Inter-relationships
400
350
300
months
250
200
150
100
50
0
1
2
3
4
5
people
6
7
8
9
Chapter 3: Key Points
• Sackman, Erikson & Grant Study  ratio between best and worst
productivity performance of programmers: 10:1
• Surgical team approach vs. hog butchering
• Team Members:
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Chief Programmer
Co-pilot
Administrator
Editor
Secretaries
Program Clerk
Toolsmith
Tester
Language lawyer
Chapter 4: Key Points
• Few architects, many implementers
• What problems can this cause?
Chapter 5: Key Points
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Role of architect vs. implementer
What issues can arise?
The second system effect (similar to goldplating)
How to avoid the second system effect?
Chapter 6: Key Points
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How to communicate with teams of hundreds?
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Weekly ½ day conference of architects + key implementers
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Same group each week
Smart people, all hands-on
Problem-solving focus
Written proposals for decisions
Clear decision-making authority
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Log of all questions & answers (website)
Early test involvement
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Problems with this?
– What about information hiding?
Chapter 7: Key Points
• Lesson of the tower of Babel
• Communication means:
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Informal
Meetings
Workbook / Notebook
Website today… how would you do it?
• Elements of success:
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Mission
Producer
Technical director/ architect
Schedule
Division of labor
Interface definitions among the parts
Chapter 8: Key Points
• Try to get real data on projects comparable in size and complexity to
yours for purposes of estimating.
Chapter 9: Key Points
• Understand your constraints. In the early days this was memory
space… memory rented for $12/K/month
• Representational v. computational equivalence (Herb Simon)
• What are the constraints today?
Chapter 10: Key Points
• Documentation for a “computer product”
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Objectives
Specifications
Schedule
Budget
Organization chart
Space allocations
Market forecasts
• Do you agree or disagree with this list? What would you add? Take
away?
Chapter 11: Key Points
• “Plan to throw one away; you will, anyhow.”
– Do you agree? What about incremental model?
• On requirement changes: “a threshold has to be established, and it
must get higher and higher as development proceeds.”
• What prevents a design from getting documented?
• The semi-U shaped bug curve (Campbell’s data)
• The fixing the fixes problem, or “program maintenance is an entropyincreasing process”
Chapter 12: Key Points
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Vehicle (aka development) machines and target machines
How would you plan machine usage?
Importance of high-level languages… examples today?
What other tools are important?
Chapter 13: Key Points
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Prevent bugs in design
Test the specification … how?
Stepwise refinement
Use debugged components … why?
Change control
Add one component at a time… why?
Chapter 14: Key Points
• “How does a project get to be a year late? …. One day at a time.”
• What makes a good milestone?
– Concrete, specific, measurable, “defined with knife-edged sharpness”
• Studies show:
– Estimates before work begins do not change
– During work, over-estimates steadily come down
– During work, under-estimates do not change until 3 weeks before
completion.
• How do you tell which slips matter most? (Pert charts, critical path)
• What Bosses need:
– Exceptions to plan that require action
– Status pictures for education
– Helps to label meetings, “status” or “action” meetings
Chapter 15: Key Points
• Documentation for the user – what would you change/add on this list?
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Purpose
Environment
Domain & Range
Functions
I/O formats
Operating instructions
Options
Running time
Accuracy and checking
• Documentation for the maintainer
• Self-documenting code
Chapter 16: Key Points
• “No silver bullet.” Advice:
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Buy rather than build
Use rapid prototyping to help establish requirements
Grow software organically (aka incremental development)
Find the good conceptual designers
• Some tough issues:
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Complexity
Conformity
Changeability
Invisibility
Chapter 17: Key Points
• OO might be the “brass bullet.”
– But lots of up-front costs
– Re-use more common at large companies than small … why?
Chapter 18
• This is Fred’s summary of the book. You
should read this one chapter if nothing else!
Quiz #3 Review
• Covers all the lectures and
all the reading to date.
• Approximate weighting:
• 50% old stuff
• 50% new since quiz #2
• Format:
• Multiple Choice
• Short Answer
• Essay
• If your average on the 1st 3 quizzes is greater than
80%, the final is optional. The final is equivalent to
a 4th quiz in weight.
Topics
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ALL of the Material on Quiz #1
ALL of the Material on Quiz #2
Why Configuration Mgmt is needed
Key Configuration Mgmt concepts
Key OO concepts
Advantages / disadvantages of OO
Cleanroom v. Waterfall process
Key cleanroom concepts
Advantages / disadvantages of
cleanroom
How to do a Demo
Testing Principles
White Box v Black Box testing
Elements of a Test Plan
Regression testing: what? why? how?
Stress testing: what? why? how?
SQA techniques … review homework
topics!
Mythical-Man Month… for sure!
Extra credit?