copyright © 1995-2003, dennis j. frailey, all rights reserved day 3, part 1, page 1 4/19/2003 day...
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Copyright © , Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 3 4/19/2003 The Overall Planning Cycle Analyze Job Manage Risks Execute Generate Detailed Plans Generate Initial Plans Measure, Manage Productivity and QualityTRANSCRIPT
Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 14/19/2003
Day 3, Part 1
Planning the Schedule
Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 24/19/2003
Outline• Basic Concepts in Schedule Planning• PERT Charts and Critical Path
Analysis• GANTT Charts • Network Charts• Critical Chain Analysis & Slack
Management• Summary
Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 34/19/2003
The Overall Planning Cycle
AnalyzeJob
Manage Risks
Execute
GenerateDetailed Plans
GenerateInitial Plans
Measure, Manage Productivity and Quality
Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 44/19/2003
EstimateSize
EstimateEffort and
Cost
EstimateScheduleEvaluate
Source InformationStatement of Work
RequirementsConstraintsStandardsProcesses
Historyetc.
WBS Size
Effort &Cost
Schedule
OKCompleteDetailedPlanning
Revise &Negotiate
Not OK
Detailed Planning - Processes
Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 54/19/2003
Architecture of SpreadsheetSize / Reuse Effort Schedules
Cocomo BasedEffort Estimate
Other EffortEstimates ...
Analogy basedSize Estimate
SoftwareReuse
Analysis
Final EffortEstimate
ProductivityBased Effort
Estimate
Generic Schedule
Effort Schedule
Other SizeEstimates ...
Final SizeEstimate
Expert BasedSize Estimate
0
5
10
15
20
25
M1 M2 M3 M4 M5 M6
TotalBuild 1Build 2
Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 64/19/2003
Basic Concepts inSchedule Planning
Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 74/19/2003
A Hypothetical(?) Scenario
I needA detailed schedule!Tell me how long it Will take and whenEach task will be
Complete.What do Ido now?Yes, sir!
Right away,Sir.
Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 84/19/2003
Three Levels of Schedule Detail
• Top Level Schedule– Generally produced during initial
planning, based on integrated master schedule for the project, project constraints, deadlines, etc.
– Focuses on how software tasks relate to the rest of the project
Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 94/19/2003
Three Levels of Schedule Detail (continued)
• Generic Schedule (top level software schedule)– Generally produced during effort
estimation, based on the process and the information gained from estimating models
– The focus is on the major (high level) software tasks and when they occur in time
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 104/19/2003
Three Levels of Schedule Detail (continued)
• Detailed Schedule– Generally produced when you are
about to execute the project or a phase of the project
– The focus is on how and when you will do the detailed work tasks
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 114/19/2003
Schedules Tend to beSomewhat Flexible
• You can vary the actual schedule to fit your conditions– You have flexibility in matching the
schedule to other project constraints– Cycle time improvement techniques
can also improve your schedule– But you can drive up cost as you
deviate too far from what is reasonable
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 124/19/2003
The Optimal Schedule...... depends on people, process, nature
of task, environment, etc. …• Different models make different
assumptions about these factors, reflecting the experience of those who developed the models
• Until we have a better theoretical foundation, experience remains the best way of predicting your optimal schedule
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 134/19/2003
• Many models use a formula• Example: Cocomo formula for optimal
schedule:
e = .35 for most projects; .38 for easy (organic); .32 for hard (embedded)
• Effort is measured in staff months• Schedule is measured in calendar
months
Schedule = 2.5 * Efforte
Total Time to Do the Job
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The Cocomo Model ofTime vs Effort
staff-days
required to do
the work
Calendar Time Allocated for the Work
Optimal Schedul
e
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 154/19/2003
Other Models VaryGrady and Caswell compare five different
sources (p34, 35) (see references)• Differences stem from:
– Type of software being developed– Schedule compression– Organizational differences– Process and methods
• Hewlett-Packard recommendations:– Measure actual data & keep for the future– Count everything (overtime, etc.)
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For Small Projects ...• Formulas fit large projects better than
small ones• And you may not have a good data
base of historical schedule information
So it may be better to estimate the time in a more detailed manner, as will be shown in the next section and in the
course exercises
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Techniques for Developing & Documenting a Detailed
SchedulePERT Charts
– Show dependencies– Can expand to show resources, timing,
and critical pathGANTT Charts
– Show timing and parallelismNetwork Charts
– Combine the benefits of PERT and GANTT– But you need a tool to manage them
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Steps of Detailed Scheduling1) Task Dependency and Flow
– Shows dependencies, but not timing2) Task Duration
– Shows minimum schedule length– Identifies the critical path
3) Critical Path Analysis– Determines what must change if the
schedule is to be reduced
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Steps of Detailed Scheduling4) Resource Requirements
– Shows manpower loading, cash flow, etc.
5) GANTT Chart – Shows relative timing– But not the dependencies
6) Network Chart – Combines GANTT and PERT
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PERT Charts &
Critical Path Analysis
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PERT“PERT” stands for
“Program Evaluation and Review Technique”
or“Performance Estimating & Reporting
Tool” (depending on which author you
read)
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PERT Origins• PERT was developed in the 1940’s
as a management tool for complex projects
• In its fullest form, PERT involves complex statistical analysis of project schedules and plans
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 234/19/2003
PERT Charts• The basic tool of the PERT
technique is the PERT Chart, which represents the schedule and resource needs of a project
• The PERT chart uses the Precedence Diagramming Method (PDM), which is similar to a flow chart, to represent the dependencies among activities
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 244/19/2003
A Minimal PERT Chart ...• Lists activities to be performed
(from WBS)• Indicates dependencies
– Activity X must precede activity Y, etc.
– This information comes in part from initial planning (life cycle analysis, organizational planning, process definition, etc.)
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 254/19/2003
Sample PERT Chart from Organizational Planning
(in Initial Planning)Prototype Final Design BuildDesignKeyboar
dCodeDesignKeyboar
dSoftware
Test
BuildKeyboardEmulation
DeliverySubcontracted SW for Numeric Key Pad
Contract
This can be produced by
hand or with a project
management or scheduling tool.
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Prototype Final Design BuildDesignKeyboard
CodeDesignKeyboardSoftware
Test
BuildKeyboardEmulation DeliverySubcontracted SW for Numeric Key Pad
Contract
An Alternative PERT Notation• Touching boxes implies dependency• Used to reduce space • Used later in this course
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• List each task on a “post-it note” or index card
• Lay out the tasks on a board• Indicate task dependencies with
lines (arcs)
Developing a PERT ChartStep 1 - Task Dependencies
Task 1 Task 3 Task 6 Task 7
Task 8Task 2 Task 5
Task 4
Task 9
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Design Test Code
Design Spec
Integrate
Develop Hardware
Code VerifyTest
Evaluating Dependencies
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“Test” Task
depends on “Code” and “Test
Code”Design Test Code
Design Spec
Integrate
Develop Hardware
Code VerifyTest
Identifying Dependencies• What depends on what?
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Design Test Code
Design Spec
Integrate
Develop Hardware
Code VerifyTest
Who needs this? (no successor)
Identifying Dependencies• What dependencies are unknown?
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Design Test Code
Design Spec
Integrate
Develop Hardware
Code VerifyTest
External task that
we depend
on
Identifying Dependencies• What external tasks do we depend
on?
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Types of PERT Dependencies
Finish to Start First task must finish before the second starts
Start to Start Second task must start x months after first starts
Finish to Finish Second task must finish y months after first finishes
x
y
Task 5Task 23
7
6Task 1 Task 3 Task 6 Task 7
Task 8
Task 4
Task 9
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 334/19/2003
With most PERTtools, you can
specify a priority amongparallel tasks
Task 1 Task 3 Task 5Task 2 Task 4
Task 5Task 1 Task 3
Task 2
Task 4
Verifying Dependencies• Do not overconstrain -- use only the
the essential dependencies• The second PERT chart represents a
much more flexible plan
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What to Learn from a Basic PERT Chart
• Identify dependencies you did not know existed
• Identify missing dependencies where you do not know the successor or the predecessor
• Identify critical dependencies, such as a hardware activity that will hold you up if it is late
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 354/19/2003
NOTEPERT Charts are a good method for developing a detailed process description as well as developing a project schedule
Prototype Final Design BuildDesignKeyboard
CodeDesignKeyboardSoftware
Test
BuildKeyboardEmulation
DeliverySubcontracted SW for Numeric Key Pad
Contract
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 364/19/2003
Steps of PERT Scheduling1) Basic PERT -- task dependency and flow
– shows dependencies, but not timing2) More Complete PERT -- task duration
– shows minimum schedule length3) Critical path
– shows what tasks contribute to minimum schedule length (what tasks need to be shortened to shorten the overall schedule)
4) Full PERT - resource requirements– shows manpower loading, resource needs,
etc.
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 374/19/2003
Developing a PERT ChartStep 2 - Task Duration
• Lay out a time line at the bottom of the board
• For each task, estimate its duration and write that information on the post-it note. – Can be minimum feasible duration or
expected duration based on availability of resources
• Place each task in its appropriate position relative to the time line
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Developing a PERT Chart Step 2 - Task Duration (continued)
• Proper placement shows earliest start date for each task [or latest start date]
20 weeks8 weeks
Minimum total time for whole activity is 26 weeksJ F M A M J J A S O N D
6weeks
8weeks
12weeks
26 weeks
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What to Learn After Durations are Added
• The first task to focus on is the very last task – Will it complete by the project
deadline?• If not, how can you make the whole
schedule shorter?• The answer starts with determining
the Critical Path
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 404/19/2003
The Critical Path is ...… the longest calendar path through
the schedule from the first to the last activity
Task A
Task CTask B
Task D
Task E
The Critical Path in the above example is A,C,D
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The Critical Path is ...… the path that must be shortened in
order to shorten the whole schedule… the path that drives schedule slips
– If a critical path task slips, the whole schedule slips
… the riskiest part of the schedule
Be especially wary when the critical path involves dependency on external tasks that you do not
control!
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• If the schedule is small, “eyeball” and determine which path is the longest.
• Otherwise a tool can be used
• Critical Path => min possible schedule
6 weeks3 weeks
5 weeks Critical PathTasks
Non-CriticalPath Tasks
Developing a PERT Chart Step 3 - Analyzing the Critical
Path
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What if the MinimumSchedule is Too Long?
• You must find a way to cut the schedule
• Begin with tasks on the critical path– Try to divide them into smaller tasks
that can be done simultaneously– Assign more resources - do them faster– Cut functionality or defer until later
• Note that when you do this you might create a different critical path
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 444/19/2003
Developing a PERT ChartStep 4 - Resource Requirements
• Determine the resource requirements of each task:– Equipment, facilities, etc.– Key personnel– Total labor effort (staff days, etc)– May also show minimum and maximum
reasonable allocations, i.e., 8 staff weeks: • minimum 2 weeks (4 people)• maximum 8 weeks (1 person)
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 454/19/2003
Resources• Write this information on the index card
or post-it-note• Vary labor totals or types of personnel
assigned to different tasks in order to meet schedule needs
8 staff weeks:2 weeks, 4 people
8 staff weeks:4 weeks, 2 people
8 staff weeks:2 weeks, 3 senior people
These options mayreduce the critical
path or even removethis task from the
critical path
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 464/19/2003
Scheduling Tools can ...… find critical path/shortest schedule… find minimum and total effort levels… do simulation of schedule to
determine likely outcomes when exact duration are indefinite
… assist in “what if” analysis of possible alternatives
… revise schedules with minimal effortSample tools: Microsoft Project®,
Primavera®
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 474/19/2003
“Schedule from the back” conceptMinimal execution times for each task
Assuming adequate staff, task E must be started at least 7 weeks before final integration, whereas task A must be started at least 11 weeks before!
Using PERT Charts to Decide on Development Sequence
Final Integration4 weeks
C1 week
D3 weeks
F4 weeks
E2 weeks
B6 weeks
A2 weeks
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 484/19/2003
Shopload Shows Resource Needs
and Allocation by Time PeriodWeek 1 2 3 4 5 6Person A 1 1 1 .5 1Person B 1 1 1 1
etc. etc. etc. etc. etc. etc. etc.Total
People2 3 5 4 4.5 3
SpecialEquip-ment A
1 2 2 1
SpecialEquip-ment B
1 1 2 1
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 494/19/2003
Suggested Notationfor Post-it Notes
Yellow– Normal Tasks
Pink or Red – External Tasks that You
Depend OnBlue
– External Tasks that Depend on You
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Schedule for Project P(sample)
J F M A M J J A S O N D
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 514/19/2003
• Gizmo hardware must arrive by June 1– We must watch their schedule
• Joe and Mary must be available 100% for this project
• Integration must wait until Sept 15• Programmers must all be available to start
on March 1• At least three test sets must be available
during the month of August
Critical Dependencies, Issues, Assumptions, and Lessons
Learned (sample)
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 524/19/2003
Steps of Detailed Scheduling1) Task Dependency and Flow
– Shows dependencies, but not timing2) Task Duration
– Shows minimum schedule length– Identifies the critical path
3) Critical Path Analysis– Determines what must change if the
schedule is to be reduced
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 534/19/2003
Steps of Detailed Scheduling4) Resource Requirements
– Shows manpower loading, cash flow, etc.
5) GANTT Chart – Shows relative timing– But not the dependencies
6) Network Chart – Combines GANTT and PERT
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 544/19/2003
GANTT Charts• These are devised from the same
data used in a PERT chart, but show the relative time phasing of the tasks instead of the dependencies
• Each “activity” box is sized to be proportional to the length of time it takes
• The boxes are lined up, usually in the order of execution, to show what is happening at what time
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 554/19/2003
Sample Gantt ChartVertical line
represents current date
Task 2
Task 3
Task 6
Task 5
Task 1
Task 7
Task 4
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 564/19/2003
Task 6
Task 5
Task 7
Does Task 6 depend on Task 5? Can Task 5 finish on time?
Gantt Chart does NOT tell you ...… task dependencies
… significance or impact of schedule slips… whether it is realistic to expect you to meet
the schedule… critical path
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 574/19/2003
Network Charts
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 584/19/2003Jan Feb Mar Apr May Jun Jul Aug
Network Chart --Combining the Pert and
Gantt•Horizontal width indicates schedule length •Arcs indicate dependencies•Horizontal position indicates scheduled
time and task parallelismTask A
Task CTask B
Task D
Task E
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 594/19/2003
Network Chart Summary• Tells you the duration of tasks and
their interdependencies. • Shows Critical Path• Can be color coded to show different
parts of the project– Software in blue, mechanical in red,
etc.• But it still cannot tell you if the
schedule is realistic
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 604/19/2003
Project Management and Scheduling Tools
• Most such tools can show a PERT or GANTT chart
• More capable tools will show a network chart, which is hard to do by hand
• But tools take a lot of work to enter data and the data changes a lot in the early steps of detailed scheduling
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 614/19/2003
Recommendations Regarding Management/Scheduling Tools• Do a PERT chart by hand and work
through the fundamental relationships• Then use a tool after things have
settled down• Select a tool carefully
– Some cannot handle the complexity of a very large project
– But the most capable tools are harder to use
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 624/19/2003
Using Network or Pert Charts to Establish a Schedule
Earliest Completion Date– Tells you how soon you can complete– Tells you the earliest you can start each task
Latest Start Date– Tells you how late you can start and still meet
the deadline– Tells you the latest you can start each task
Critical Chain Analysis– Adds analysis of critical resource needs– Can help you manage to meet short cycle time
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 634/19/2003
Earliest Completion Date
A, C, E, F can slip without hurting schedule
E4 weeks
Final Integration4 weeks
G3 weeks
D6 weeks
A3 weeks
B4 weeks
C2 weeks
F2 wks
17 weeks min.
Earliest Start DateLater Start Date
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 644/19/2003
Latest Start Date
• A, C, E, F can start late without hurting schedule• B, D, G, Final must start as shown, since on critical
path
Final Integration4 weeks
G3 weeks
D6 weeks
A2 weeks
B4 weeks
C2 weeks
F2 wk
E4 weeks
17 weeks min.
Earlier Start DateLatest Start Date
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 654/19/2003
Critical Chain Analysis&
Slack Management
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 664/19/2003
• A Critical Resource is a resource that is required on each of two or more tasks– A piece of
equipment– An individual with
unique skills• If shared, each task
gets only part time use
?
Youare essential
to myproject
Myproject willfail without
you
Critical Resources
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 674/19/2003
• If two tasks need a resource, one must give it up or both must run slower
• But it is tempting to fantasize that you can share resources without such high waste
Sharing a Resource MeansLess Efficiency
Percent Use AvailabilityWaste
100% 85% 15%50%+50% 40%+40% 20%33%+33%+33% 25%+25%+25% 25%25%+.... 17.5%+.... 30%
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 684/19/2003
Using Critical Resources• If the resource is critical, it is also
known as a constraint• The fundamental rule of constraint
management is that you should maximize the efficiency of the constraint
• Which means you avoid overusing constraints and wasting time on inefficient sharing
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 694/19/2003
If Task B needs a resource that is also needed by Task A then Task B is on the
Critical Chain
The Critical Chain• The critical chain consists of all
tasks using resources that are needed on the critical path
Task A
Task CTask B
Task D
Task E
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 704/19/2003
Critical Chain Analysis• Start with Latest Start Date schedule • Mark critical path tasks as “on the
critical chain” & identify resources needed for these tasks
• If also needed elsewhere in parallel tasks, mark those tasks as “critical chain” tasks
• Reschedule those tasks earlier, so there is no conflict of resources
• This may change the critical path!
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 714/19/2003
Conventions for Critical Chain Analysis
ConflictEarlier Start Date
Latest possible
Start Date
NormalTasks
Critical Pathand
Critical Chain
Critical Chainbut Not
Critical Path
CriticalPath Tasks
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Example of Critical Chain Analysis
G and F need the same critical resourceSo F and its predecessors (E, C) must be started
sooner
A3 weeks
Final Integration4 weeks
G3 weeks
D6 weeks
B4 weeks
E4 weeks
C2 weeks
F2 wk
17 weeks min.
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 734/19/2003
A Further Example
• A and C cannot proceed in parallel• This changes the critical path and lengthens
the schedule!
H4 wks
G3 wksA
3 wks
E4 wks
C2 wks
F2 wks
B4 wks
D6 wks 18 weeks
minimum
Suppose A and C need the Same Critical Resource
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 744/19/2003
Other Schedule Management Techniques
• Do more careful monitoring of critical path and critical chain tasks
• Start critical chain tasks as soon as you can - to provide maximum risk control
• DO NOT allow people to include slack time in their task schedules. All slack should be held in reserve by a higher level manager
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 754/19/2003
Example of Slack Management Problem
Final Integration4 weeks
G3 weeks
E4 weeks
C2 weeks
Final Integration4 weeks
G3 weeks
E4 weeks
C2 weeks
Plan: C and E allow slack to reduce risk
Actual: C and E wait until last possible minute to start
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 764/19/2003
What Might Really Happen
Final Integration4 weeks
G5 weeks
E4 weeks
C2.5 weeks
Reality: C and G slip a little bit …
C’s slip is absorbed by E’s slackBut G’s slip causes the whole project to slip 2 weeks
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 774/19/2003
Slack Management
Final Integration4 weeks
G5 weeks
E4 weeks
C2.5 weeks
Actual - Slack can be applied to any task that slips, so the project stays on schedule
Final Integration4 weeks
G3 weeks
E4 weeks
C2 weeks
Plan: C and E have no slack
Slack - 4 wks
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 784/19/2003
• Critical path analysis identifies what tasks must be shortened to shorten the overall schedule
• Adding resource requirements enables you to decide on sequencing and when to schedule tasks and resources
• GANTT shows relative timing but not dependencies, flow
• Network chart shows both, but requires a more capable tool
Summary Schedule Estimation &
Planning
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 794/19/2003
• Critical Chain shows resource conflicts between critical path tasks & other tasks
• Critical Resources must be managed to avoid impact on critical path
• Critical Chain Analysis shows which tasks must be started earlier in order to avoid resource conflicts
• Slack Management gives maximum risk control and shortest cycle time
SummarySchedule Estimation &
Planning
Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 3, Part 1, Page 804/19/2003
1) Brassard, Michael, The Memory Jogger Plus+, Goal/QPC, Methuen MA, 1989.
2) Goldratt, Eliyahu M. & Jeff Cox, The Goal, (North River Press, 1984.) Also Theory of Constraints and It’s Not Luck.
3) Thayer, Richard H., ed., Software Engineering Project Management, IEEE Computer Society Press, 1994.
4) U. of West Florida, PERT Home page, http://www.uwf.edu/~coehelp/studentaccounts/rnew/perthome.html
ReferencesSchedule Estimation &
Planning