Project Scheduling (1)
Tran Van Hoai
Faculty of Computer Science & Engineering
HCMC University of Technology
2010-2011
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What is project management?
Project management (PM) is the discipline of
planning, organizing, securing and managing
resources to bring about the successful
completion of specific engineering project goals
and objectives
• Project is not business as usual (operations)
– Operations means repetitive, permanent, semipermanent
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Primary challenges of PM
• To achieve all of the predefined project goals
• To honor the preconceived project constraints
– Typical constraints are scope, time, and budget
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Brief history (1)
• 1900: PM has been practiced in
civil engineering projects
• 1910: Gantt chart, proposed by
Henry Gantt
• 1916: 5 management functions,
proposed by Henri Fayol
• <1950s: PM performed by Gantt
charts, and informal techniques
and tools
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Brief history (2)
• 1950: mathematical project scheduling
models developed
– Critical Path Method (CPM)
– Program Evaluation and Review Technique
(PERT)
• Technology developed
– Certification
– Standard
– Organizations
–…
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Approaches (1)
• Traditional approach
Waterfall
model in
Software
Development
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Approaches (2)
• Critical Chain Project Management (CCPM)
– More emphasis on resources
– Based on Theory of Constraints (Goldratt [1984])
• Guarantee that resources are ready when critical chain
tasks must start
• Extreme Project Management (XPM)
– PERT-based models do not work well for multiproject company environment
– to manage very complex and very uncertain
projects
• “lightweight” models, human interaction management
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Approaches (3)
• Event chain methodology
– Complement CPM and CCPM methodologies
– identify and manage events and event chains to
cope with uncertainty
• PRINCE2
– Structured approach
– Automatic control
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Approaches (4)
• Process-based
management
– Maturity models:
CMMI (Capability
Maturity Model
Integration)
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Processes (stages)
•
•
•
•
•
Initiation
Planning or development
Production or execution
Monitoring and controlling
Closing
In R&D projects (much explorative elements),
these stages may be supplemented with decision points
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Initiation (1)
• To determine the nature and scope of the
project
– Must be performed well
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Plan for initiation
• Analyzing the business needs/requirements in
measurable goals
• Reviewing of the current operations
• Financial analysis of the costs and benefits
including a budget
• Stakeholder analysis, including users, and
support personnel for the project
• Project charter including costs, tasks,
deliverables, and schedule
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• determining how to plan (e.g. by level of detail or rolling
wave)
• developing the scope statement
•• To
selecting
plan time,
the planning
cost team
and resources adequately to
• estimate
identifying deliverables
and creating
theto
work
breakdown
the
work
needed
and
effectively
structure
during needed
projecttoexecution
• manage
identifyingrisk
the activities
complete those
deliverables and networking the activities in their logical
sequence
• estimating the resource requirements for the activities
• estimating time and cost for activities
Planning & Designing
• developing the schedule
• developing the budget
• risk planning
• gaining formal approval to begin work
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Scheduling
Define work
activities
Sequence work
activities
Schedule
activities
Identify work
activity
resource
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Estimate work
activity
duration
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Executing
• To complete the work defined in the project
management plan to accomplish the project's
requirements
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Monitoring & Controlling
• To observe project execution so that potential
problems can be identified in a timely manner
and corrective action can be taken, when
necessary, to control the execution of the
project
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Closing
• formal acceptance of the project
• to archive of the files and to document lessons
learned
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Project scheduling - definition
• Project =
– Collection of tasks (activities)
– A task requires other tasks accomplished before it
starts (precedence relations)
– Factors affecting completion time
• Resources
• Detail level of the project target
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Objectives
• Determining a schedule leading to earliest
completion time for entire project
• Calculate the likelihood a project completed
within a certain time period
• Finding minimum cost to finish the project by
a certain date
• Finding a schedule smoothing out resource
allocation
• …
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Klonepalm 2000 activity description
Activity
Manufacturing activities
Training activities
Advertising activities
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Description
A
Prototype model design
B
Purchase of materials
C
Manufacture of prototype model
D
Revision of design
E
Initial production run
F
Staff training
G
Staff input on prototype models
H
Sales training
I
Preproduction advertising campaign
J
Post-redesign advertising campaign
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Precedence relations
Activity
A
B
C
D
E
F
G
H
I
J
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Immediate predecessors
A
B
G
D
A
C,F
D
A
D,I
Estimated completion
time (days)
90
15
5
20
21
25
14
28
30
45
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PERT/CPM network
• Network representation reflecting precedence
relations
• Network G = (V,A)
– V: vertex set = set of activities,
• vi = estimated completion time
– A: arc set = set of precedence relations
• aij if activity j is preceded by activity i
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Klonepalm 2000 PERT/CPM network
B
15
A
90
E
21
C
5
F
25
G
14
I
30
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D
20
H
28
J
45
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PERT/CPM approach
• PERT/CPM analyses are
– To determine minimal possible completion time
– To determine a range of start and finish times for
each activity (such that project completed in
minimal time)
• Earliest times (ES,EF)
– Computed by forward pass
• Latest times (LS,LF)
– Computed by backward pass
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Earliest/Latest Start/Finish Times
= ES(X)
+ Weight(X)
ES(A)EF(X)EF(A)
LF(A)
LS(A)
LF(X) = LS(X) + Weight(X)
ES(X) = MAXY=immediate predecessor of X{EF(Y)}
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ES/EF Sequence
90,105
149,170
105,110
B
15
E
21
C
5
0,90
90,115
A
90
F
25
129,149
115,129
G
14
90,120
D
20
149,177
H
28
149,194
I
(Minimal) Estimated
completion time =J 194
30
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LS/LF Sequence
90,105
B
15
95,110
0,90
A
90
0,90
E
21
C
5
110,115
90,115
115,129 129,149
F
25
90,115
90,120
G
14
115,129
I
30
D
20
129,149
173,194
149,177
H
28
166,194
149,194
J
45
119,149
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149,170
105,110
149,194
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Slack times
• To measure the amount of time an activity can
be delayed from its ES without delaying the
project’s estimated completion time
Slack(X) = LS(X) – ES(X)
Critical path are those with slack time = 0
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Critical path
90,105
B
15
95,110
0,90
A
90
0,90
149,170
105,110
E
21
C
5
110,115
90,115
115,129 129,149
F
25
90,115
90,120
G
14
115,129
D
20
129,149
Critical
path = longest path
I
30
119,149
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173,194
149,177
H
28
166,194
149,194
J
45
149,194
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Analyses of possible delays
• What if an activity on critical path is delayed ?
• What if an activity not on critical path is
delayed ?
• What if multiple delays occur ?
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