Unit 10 – Network Logic and Scheduling
April 2007 | Project Management | Wilhelm F. Neuhäuser
© IBM Corporation 2007
Project Management
Agenda
Unit 10: Network Logic and Scheduling
Objectives
A practical approach to project scheduling
Schedule types
Project scheduling
Network analysis
Leveling
Rolling-wave planning concept
Gantt chart
Milestone chart
Key Messages - Unit 10
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Unit 10 | Network Logic and Scheduling
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Project Management
Objectives
At the end of this module, you will be able to Define networks and schedules
Identify various types of logic networks and
approaches, and weigh their relative merits for
specific development projects
Use logic networks and scheduling approaches
appropriate to their particular projects
Integrate a WBS into a logic network and
determine a schedule for that network
Incorporate risk into scheduling considerations
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Unit 10 | Network Logic and Scheduling
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Project Management
A Practical Approach to Project Scheduling
Working rules
Time is usually the critical factor
Scheduling and risk management functions are the
foundation for project control
You should be able to predict probable delays, initiate steps,
and always include in a report Impact of the delay
Steps to be taken to avoid or reduce delay
"Key events" (to be defined) and milestones are to be
recognized as deadlines
Anyone who is not fulfilling his or her timely obligation should
be immediately notified
The project manager is not a "schedule mechanic"
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Project Management
A Practical Approach to Project Scheduling (continued)
The tools
Use a project management tool (like MS Project) for
scheduling based on the common WBS
Have internal and external suppliers, project team members,
and business partners participate in the scheduling
(according to the main project schedule), identify who is
allocated to a task, and report on agreed-upon key events
Make obligations such as submitting data, approving
deliverables, and meeting other obligations, an integrated
part of the project schedule
Emphasize key events more than activities
Strictly define events regarding contents so that cause of a
delay can be concisely and quickly identified
Project management is management of interfaces!
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Unit 10 | Network Logic and Scheduling
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Project Management
Schedule Types
Networking
Activity-on-arrow (AOA)
Precedence diagram method (PDM)
Gantt chart
Milestone chart
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Unit 10 | Network Logic and Scheduling
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Project Management
Project Scheduling
Tasks
Start
Review
1. Design
2. Build
Start
KEY:
Review
Complete
In progress
3. Test
1
Tasks
Approve
Approve
Start
2
3
4
5
7
6
Task 1
8
Network
chart
Gantt
chart
Task 2
Task 3
7
Complete
Milestone
chart
Unit 10 | Network Logic and Scheduling
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Project Management
Network Scheduling
Schedule flows from WBS work packages' planned
or actual duration
Schedules may be driven by amount of resources
required
Schedule is a major element of project baseline
(along with expense and technical considerations)
Shows time to finish and activity interdependencies
Provides greatest amount of information - useful for
detailed analysis
Two types
Activity-on-arrow
Precedence diagram method
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Project Management
Essential Scheduling Data (Example)
Activities and Times
Activity
a
b
c
d
e
f
g
h
i
j
k
l
m
n
9
Initiate project
Assign PM
Establish constraints
Form project development team
Develop project schedules
Prepare expense estimates
Conduct process training
Design integrated project file (IPF)
Assign resources
Prepare business case
Write integrated project plan (IPP)
Finalize IPP
Conduct IPF training
Reproduce documents
Unit 10 | Network Logic and Scheduling
Immediately
Preceding Activity
a
a
b
d
d
d
b
c,e
g
f,i,j
k
h,g
m
Expected Completion
Time (days)
5
2
6
12
10
9
5
9
1
2
3
9
7
8
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Project Management
Networks can be used for CPM and Slack Analysis
Activity-on-arrow
6
c
Establish
constraints
Start
5
a
Initiate project
2
b
Assign PM
12
d
Form project
development team
10
e
Develop
project
schedule
1
i
Assign
resources
3
9
k
f
Write IPP
Prepare expense
estimate
2
5 g
j
Conduct
Prepare
process
business case
training
9
h
Design IPF
9
l
Finalize
IPP
Concept
check point
8
n
Reproduce
documents
7
m
Conduct
IPF training
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Unit 10 | Network Logic and Scheduling
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Project Management
Precedence Diagram Method
(e)
Develop
project
schedule
Start
(a)
Initiate
project
(i)
Assign
resources
(c)
Establish
constraints
(b)
Assign
PM
(d)
Form
PDT
(f)
Prepare
expense
estimates
(l)
Finalize
IPP
Finish
check point
(j)
Prepare
business
case
(m)
Conduct
IPF
training
(h)
Design
IPF
(k)
Write
IPP
(n)
Reproduce
documents
(g)
Conduct
process
training
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Unit 10 | Network Logic and Scheduling
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Project Management
Basic Scheduling Terminology
Activity: A task (work package) performed over a
period of time; a specific piece of defined work
from WBS
Milestone: Zero time duration activity
Relationships: Dependencies that exist between
activities
Free float: The amount of time an activity can be
delayed without delaying the early start of any
immediately following activities
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Project Management
Basic Scheduling Terminology (continued)
Total float: The amount of time that an activity may
be delayed from its early start without delaying the
project finish date
Critical path: Longest time period from start to
completion of a project; also the shortest total length
of the project
Lag: Imposed delay between the start or finish of one
activity and the start or finish of another
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Unit 10 | Network Logic and Scheduling
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Project Management
Basic Scheduling
Earliest an activity
can start, based on
project logic
Earliest an activity
can finish, based on
Early Start
Early Start
Early Finish
ES
EF
Activity name
Duration
14
LS
LF
Late Start
Late Finish
Latest an activity
can start, without
delaying project
completion, based
on Late Finish
Latest an activity
can finish, without
delaying project
completion, based on
project end date
Unit 10 | Network Logic and Scheduling
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Project Management
Types of Relationships
Finish
Start
Activity
1
Activity
2
Activity 1 must be totally finished before Activity 2
can start: traditional
Example: Define requirements (Activity 1),
perform DCUT - design, code, unit test (Activity 2)
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Unit 10 | Network Logic and Scheduling
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Project Management
Types of Relationships (continued)
Finish
Finish
Activity
1
Activity
2
Activity 2 cannot finish until Activity 1 finishes
Example: Activity 2 (reviewing the high-level
design) cannot be finished until Activity 1 (writing
the high-level design) is finished
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Unit 10 | Network Logic and Scheduling
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Project Management
Types of Relationships (continued)
Start
Start
Activity
1
Activity
2
Activity 2 cannot start until Activity 1 begins; a lag of n
time units can be defined
Example: Reviewing the specifications (Activity 2) can
begin after writing the specifications (Activity 1) begins
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Unit 10 | Network Logic and Scheduling
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Project Management
Hard Coding Relationship Constraints
Start no earlier than (SNET)
Start no later than (SNLT)
Finish no earlier than (FNET)
Finish no later than (FNLT)
Must start on (MSO)
Must finish on (MFO)
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Unit 10 | Network Logic and Scheduling
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Project Management
Using the Hard Constraints
Cautions
They will override the normal critical-path
calculations
They remove naturally occurring float in your
schedule
Useful for Creating milestone charts
Positioning activities to eliminate excessive float
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Unit 10 | Network Logic and Scheduling
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Project Management
Network Calculations
Forward pass through the network (beginning at
project start) determines Early Start and Early
Finish for each activity
Backward pass through the network (beginning at
project finish) determines Late Finish and Late
Start for each activity
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Unit 10 | Network Logic and Scheduling
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Project Management
Forward Pass
Established: Project Start date
Project Start date is the Early Start date for first
network activity
Work from left to right, top to bottom of the network
When an activity has multiple predecessors (P),
select highest Early Finish date as Early Start date
of successor (S)
Calculations
ESP + Duration = EFP
EFP + Lag = ESS
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Unit 10 | Network Logic and Scheduling
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Project Management
Forward Pass (continued)
Full precedence diagram
ES
1
EF
8
ES
8
EF
14
ES
14
EF
17
LS
LF
LS
LF
LS
LF
Duration=7
Task A
Duration=6
Task C
Duration=3
Task G
ES
17
EF
19
Duration=2
Task H
Start
LS
ES
1
EF
4
Duration=3
Task B
LS
LF
ES
4
EF
7
Duration=3
Task D
LS
LF
ES
4
EF
6
LS
LF
ES
7
Finish
LF
EF
10
Duration=3
Task E
LS
LF
Duration=2
Task F
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Unit 10 | Network Logic and Scheduling
© IBM Corporation 2007
Project Management
Backward Pass
Established: Project Finish date (from last activity
in Forward Pass)
Project Finish date is the Late Finish date for last
network activity in the Backward Pass
Work from left to right, top to bottom of network
When a predecessors (P) has multiple successors
(S), select the lowest Late Start date as the Late
Finish of the predecessor
Calculations
LFS - Duration = LSS
LSS - Lag = LFP
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Unit 10 | Network Logic and Scheduling
© IBM Corporation 2007
Project Management
Backward Pass (continued)
Full precedence diagram
ES
1
EF
8
ES
8
EF
14
ES
14
EF
17
1
LS
8
LF
8
LS
14
LF
14
LS
17
LF
Duration=7
Task A
Duration=6
Task C
Duration=3
Task G
ES
17
EF
19
Duration=2
Task H
Start
17
LS
ES
1
EF
4
Duration=3
Task B
8
LS
11
LF
ES
4
EF
7
Duration=3
Task D
11
LS
14
LF
ES
4
EF
6
12
LS
14
LF
ES
7
Finish
19
LF
EF
10
Duration=3
Task E
14
LS
17
LF
Duration=2
Task F
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Unit 10 | Network Logic and Scheduling
© IBM Corporation 2007
Project Management
Float/Slack
Float = Late Finish - Early Finish
or
Float = Late Start - Early Start
Float/Slack > 0 (time is available)
Float/Slack = 0 (path is critical)
Float/Slack < 0 (project is behind schedule/critically late)
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Unit 10 | Network Logic and Scheduling
© IBM Corporation 2007
Project Management
Critical Path
Longest of all paths through the project
Shortest time to complete the project
Path with least float/slack time
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Unit 10 | Network Logic and Scheduling
© IBM Corporation 2007
Project Management
Process for Computing Critical Path Network Schedule
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Step 8
Step 9
Step 10
Step 11
Step 12
Step 13
Step 14
Step 15
27
Establish a "begin" activity
Identify all activities that can begin immediately (that is, that have no
predecessors)
Identify what, as a result of the activities being started/completed, can now
start/end
Complete process until all predecessors and successors have been
identified
Make "end" the final activity
Calculate the forward pass; when multiple dates must be passed forward,
select the latest date
Establish the natural end date of the project
Calculate the backward pass; when multiple dates must be passed
backward, select the earliest date
Calculate float
Identify the critical path and paths with low levels of float
Restrict the project by adding any intermediate end date constraints
Recalculate the backward pass
Recalculate float
Identify the critical path and paths with low levels of float
Use networking techniques to eliminate any negative float
Unit 10 | Network Logic and Scheduling
© IBM Corporation 2007
Project Management
Benefits of Critical Path Method
Shows explicit relationships
Coordinates "big picture"
Lays out flow of work
Encourages careful task analysis
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Unit 10 | Network Logic and Scheduling
© IBM Corporation 2007
Project Management
Exercise: Precedence Diagram Method
12
14
8
B
D
G
FS+6
8
14
12
A
H
I
16
13
C
E
19
SS+10
F
1. Calculate the forward and backward passes
2. Identify the critical path
3. Calculate the float for each path
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Unit 10 | Network Logic and Scheduling
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Project Management
Network Analysis
Is the critical path what I expected?
How much float is in the schedule?
Do I need to do anything about it?
Should activities with large amounts of float be rescheduled?
Are there any near-critical paths?
What risks are on the critical path?
Danglers
No predecessor?
No successor?
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Unit 10 | Network Logic and Scheduling
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Project Management
Network Analysis (continued)
Analyze against target costs and schedule
Resource usage
Overallocated ?
Availability ?
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Unit 10 | Network Logic and Scheduling
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Project Management
Making Up Time in a Schedule During Planning
Change the relationships among tasks so that the
critical path is shorter (fast tracking)
Do tasks in parallel, instead of sequentially
Contract out tasks that are being done in series because of
lack of available personnel
Change approach to work, creating a different set of
interrelated tasks with shorter critical path
Change a Finish-Start relationship to a Finish-Finish
relationship
Change a date constraint so a task on the critical path
can start or end sooner
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Unit 10 | Network Logic and Scheduling
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Project Management
Leveling
Resource leveling
Schedule the project inn such a way as to use
resources most effectively
Schedule the project to minimize idle time for
resources
Avoid committing resources in such a way that
exceeds resource capacity
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Unit 10 | Network Logic and Scheduling
© IBM Corporation 2007
Project Management
Leveling (continued)
Resource allocation leveling
Distribution of resources to the schedule
Resource constraints vs. time constraints
Priority rules for resource allocation
Examples of resource allocation
Use of analysis of resource histograms
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Unit 10 | Network Logic and Scheduling
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Project Management
Resource Utilization 1
Weeks
Tasks
Initiate project
1
2
2
Assign PM
3
Establish constraints
2
Form project development team
3
4
5
6
7
9
Total
2
3
2
4
4
4
8
Develop project schedules
2
2
4
Prepare expense estimates
2
2
4
Conduct process training
4
Design integrated project file (IPF)
4
3
3
Prepare business case
4
Write integrated project plan (IPP)
4
3
Finalize IPP
3
3
3
6
Conduct IPF training
3
3
Reproduce documents
4
4
Totals
35
8
2
Unit 10 | Network Logic and Scheduling
5
9
4
8
8
10
3
3
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© IBM Corporation 2007
Project Management
Resource Histogram 1
10
Number of Resources
(max = 8)
8
6
4
2
0
1
2
3
4
5
6
7
8
9
Weeks
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Unit 10 | Network Logic and Scheduling
© IBM Corporation 2007
Project Management
Review Float
Late Start/Late Finish dates
1
2
3
4
Assign PM
6
7
8
9
Establish constraints
Float
Initiate
project
5
Form project dev. team
Float
Develop project schedule
Write IPP
Finalize IPP
Design IPF
Prepare expense estimate
Float
Conduct
IPD
training
Prepare
business
case
Float
Conduct
IPF
training
Float
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Unit 10 | Network Logic and Scheduling
Reproduce
documents
© IBM Corporation 2007
Project Management
Resource Utilization 2
Weeks
Tasks
Initiate project
1
2
Assign PM
2
3
4
5
6
7
8
3
2
Form project development team
Total
2
3
Establish constraints
4
2
4
4
8
Develop project schedules
2
2
4
Prepare expense estimates
2
2
4
4
4
Conduct process training
Design integrated project file (IPF)
3
3
Prepare business case
4
4
Write integrated project plan (IPP)
3
3
Finalize IPP
3
Conduct IPF training
3
Reproduce documents
Totals
38
9
2
Unit 10 | Network Logic and Scheduling
3
4
9
6
8
7
6
3
6
3
4
4
7
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© IBM Corporation 2007
Project Management
Resource Histogram 2
10
Number of Resources
(max = 8)
8
6
4
2
0
1
2
3
4
5
6
7
8
9
Weeks
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Unit 10 | Network Logic and Scheduling
© IBM Corporation 2007
Project Management
Rolling-Wave Planning Concept
Detailed planning of entire project may not be
practical or possible
Plan finite increments at outset based on project
phases (work packages of early efforts, planning
packages beyond)
Expand the detailed planning window as each
project phase is completed; for longer project
phases, plan in increments of 90 days
The planning window will vary based on size,
length, complexity, and type of development project
(for example, new, derivative, refresh)
Remember to include planning time in project plan
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Unit 10 | Network Logic and Scheduling
© IBM Corporation 2007
Project Management
Gantt Chart
Shows start, finish, and duration of various activities
Easiest schedule to make
Most common scheduling tool
Provides tremendous amounts of information very useful for analysis
Most understandable for people lacking formal
project management training
Software capabilities greatly enhance usefulness for
analysis
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Unit 10 | Network Logic and Scheduling
© IBM Corporation 2007
Project Management
Sample Gantt Chart
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Unit 10 | Network Logic and Scheduling
© IBM Corporation 2007
Project Management
Milestone Chart
Reflects project status of key events over time
Activity
Concept Checkpoint
Plan Checkpoint
DCUT start
SVT start
Delivery to customer
January
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Unit 10 | Network Logic and Scheduling
February
March
April
May
June
© IBM Corporation 2007
Project Management
Before Finalizing Schedule, Examine...
Roles: Is there a complete set of roles for each task?
Actions: Add roles where needed
People: Who will fill these roles?
Action: Assign people
Skills: Do the people assigned possess the needed skills?
Action: Add or change people or re-estimate the duration to
allow time to improve skill levels
Availability: When will the people really be available?
Action: Reschedule around nonavailable time
Action: Change utilization assumptions to adjust duration
Action: Add more people
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Unit 10 | Network Logic and Scheduling
© IBM Corporation 2007
Project Management
Key Messages
Time is usually a critical factor in development projects
A variety of tools can evaluate and map out schedules
Project managers must know how to evaluate their
schedules and the potential for schedule improvement
45
Unit 10 | Network Logic and Scheduling
© IBM Corporation 2007
Project Management
Exercise: Precedence Diagram Method
12
14
8
B
D
G
FS+6
8
14
12
A
H
I
16
13
C
E
19
SS+10
46
Unit 10 | Network Logic and Scheduling
F
© IBM Corporation 2007