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CS 501: Software Engineering
Lecture 4
Project Management
CS 501 Spring 2002

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Administration
Next Tuesday
• Short Lecture: Managing Code and Documentation (Harris)
• Quiz
45 minutes open book and notes
2 questions on lectures and readings to date
CS 501 Spring 2002

OS 360
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The operating system for the IBM 360 was two years late .
Question: How does a project get two years behind schedule?
Answer: One day at a time!
Fred Brooks Jr., The Mythical Man Month
CS 501 Spring 2002

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The Aim of Project Management
To complete a project:
• On time
• On budget
• With required functionality
• To the satisfaction of the client
• Without exhausting the team
CS 501 Spring 2002

Terminology
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Deliverable
Work product that is provided to the customer (report, presentation, documentation, code, etc.)
Activity
Part of a project that takes place over time.
Event
The beginning or end of an activity.
Milestone
Completion of a specified set of activities (e.g., delivery of a deliverable)
CS 501 Spring 2002

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The Project Manager
• Create and maintain the schedule.
• Track progress against schedule.
• Keep some slack in the schedule (minimize risk ).
• Continually make adjustments:
Start activities before previous activity complete
Sub-contract activities
Renegotiate deliverables
• Keep senior management informed ( visibility ).
CS 501 Spring 2002

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Project Planning Methods
The Critical Path Method, Gantt charts, Activity bar charts, etc. are roughly equivalent.
These methods are best when:
• Model is updated regularly (e.g., monthly)
• The structure of the project is well understood
• The time estimates are reliable
• Activities do not share resources
CS 501 Spring 2002

Example: An Open University Course
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Deliverables:
1
4
16 Written texts (bound in pairs)
8 Television programs
8
4
Radio programs
Computer programs
Home experimental kit (scientific calculator)
Assignments and sample solutions
CS 501 Spring 2002

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Scheduling: Activity Graph
An activity
A dummy activity
An event
A milestone
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Activity Graph (part)
START other activities
Revise
Unit 3
Edit
Unit 3
Print
Unit 3
Mail
Unit 3
END
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CS 501 Spring 2002

Activity Graph (continued) other activities
START
Revise
Unit 3
Edit
Unit 3 other activities
Revise
Unit 4
Edit
Unit 4
Typeset
Unit 3
Print
Units 3/4
Mail
Units 3/4
Typeset
Unit 4
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CS 501 Spring 2002

START
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Activity Graph (continued)
Script
TV 2
Edit
Unit 3
Make
TV 2
Edit
Unit 4
Prototype Computer 1
Mail
Document
Computer 1 Program
Computer 1
CS 501 Spring 2002

Background
PERT
Program Evaluation and Review Technique introduced by the
U.S. Navy in 1957 to support the development of its Polaris submarine missile program.
PERT/Time
Activity graph with three time estimates (shortest, most probable, longest) on each activity to compute schedules.
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PERT/Cost
Added scheduling of resources (e.g., facilities, skilled people, etc.)
CS 501 Spring 2002

Critical Path Method
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Uses Activity Graph with single time estimate for each activity to estimate, for each event: earliest start date latest start data and for each activity: slack
The standard method for managing large construction projects.
On big projects, activity graphs with more than 10,000 activities are common place.
CS 501 Spring 2002

Time Estimates for Activities (Weeks)
15
1
4
12
12
3
4
3
2
4
2
3
3
6
1
2
8
1
CS 501 Spring 2002

Earliest Start Dates
16
0
1
1
3
12
4
12
12
12
3
4
5
15
2
15
17
2
4
4
17
19
3
3
20
22
6
1
23
1
23 24
25
2
8
8
17
CS 501 Spring 2002

Latest Start Dates
17
10
0
11
4
1
3
12 15
12
12
14
3
18
17
4
13
2
4
2
19
20
17
3
20
3
6
23
1
24
1
25
2
22
17
8
CS 501 Spring 2002

Critical Path
18
0 / 0
1 / 11
12 / 12 15 / 15 17 / 17
22 / 23 23 / 24
25 / 25
12 / 14 17 / 17
4 / 13
19 / 20
17 / 17
CS 501 Spring 2002

Slack
19
1 / 11
Slack of activity
= (latest start) end
- (earliest start) begin
- (time estimate)
0 / 0
1
10
12 / 12
4
10
15 / 15 17 / 17
12
0
12
4
2
9
12 / 14
4 / 13
3 0
2
3
17 / 17
2 0
2
0
1
19 / 20
3
0
4 9
3
1
3
6
22 / 23
2
1
1
2
5
23 / 24
1 1
25 / 25
0
8
17 / 17
CS 501 Spring 2002

Estimating the Time for an Activity
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With experienced staff, estimating the actual time to carry out a task is usually fairly accurate, but ...
The little bits and pieces are underestimated
• The time from almost "done" to completely "done" is much longer than anticipated. (There's just one thing to tidy up. I need to put the comments into better shape. I really should get rid of that patch.)
• The distractions are not planned for.
(My system crashed and I decided to upgrade the software. My child's school was closed because of snow. I spent the day showing visitors around.)
Some things have to be done twice.
CS 501 Spring 2002

Start-up Time
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On a big project, the start-up time is typically three to six months:
• Personnel have to complete previous projects (fatigue) or be recruited.
• Hardware and software has to be acquired and installed.
• Staff have to learn new domain areas and software (slow while learning).
• Clients may not be ready.
CS 501 Spring 2002

Experience with Critical Path Method
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Administrative computing department at Dartmouth used the
Critical Path Method for implementation phase of major projects.
Experience: Elapsed time to complete projects was consistently
25% to 40% longer than predicted by model.
Analysis:
• Some tasks not anticipated (incomplete understanding)
• Some tasks had to be redone (change of requirements, technical changes)
• Key personnel on many activities (schedule conflicts)
• System ZZZ (non-billable hours)
CS 501 Spring 2002

Adding Resources to Activity Graph
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Each activity is labeled with resources, e.g.,
Number of people (e.g., 2 Java programmers)
Key personnel (e.g., chief system architect)
Equipment (e.g., 3 servers with specified software)
Facilities (e.g., video conference center)
Each resource is labeled with availability, e.g.,
Hiring and training
Vacations
Equipment availability
CS 501 Spring 2002

Using Critical Path Method for
Resources
Assume every activity begins at earliest start date:
In each time period, calculate: resources required resources available
Identify shortage / surplus resources
Adjust schedule acquire extra staff (e.g., consultants) rearrange schedule (e.g., change vacations) change order of carrying out activities
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The earlier that a problem is known, the easier it is to fix.
CS 501 Spring 2002

Key Personnel
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In computing, not all people are equal
• The best are at least 5 times more productive.
• Some tasks are too difficult for everybody.
Adding more people adds communications complexity
• Some activities need a single mind.
• Sometimes, the elapsed time for an activity can not be shortened.
What happens to the project if a key person is sick or quits?
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Key Personnel: Schedule for Editor
Earliest Start Date
Weeks 15-16
Weeks 17-18
Weeks 19-20
Weeks 21-22
Week 15
Week 17
Week 19
Week 21
Weeks 18-19
Activity
Edit Unit 3
Edit Unit 4
Edit Unit 5
Edit Unit 6
Review draft of Unit 7
Review draft of Unit 8
Check proofs of Unit 3
Check proofs of Unit 4
Vacation
CS 501 Spring 2002

Flexibility: Open University Example
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Schedule: Dates for broadcasting TV and radio programs are fixed. Printing and mailings can be accelerated if overtime is used.
Functionality: The course team can decide what goes into the components of the course.
Resources: The size of the course team can be increased slightly.
CS 501 Spring 2002

Value of Scheduling Tools
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Planning discipline
• Identify all activities and inter-relationship
• Provide schedule for each resource (identify clashes)
• Early warning of difficulties (e.g., timing of equipment purchase)
Routine updating of schedule
• Focus on key milestones
• Visibility for management
Weekly staff meeting -- What did we expect to accomplish?
What did we accomplish? What is expected for next week?
CS 501 Spring 2002