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Unit 10 – Network Logic and Scheduling
October 2003 | Project Management | Wilhelm F. Neuhäuser
© IBM Corporation 2003
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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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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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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Schedule Types
 Networking
 Activity-on-arrow (AOA)
 Precedence diagram method (PDM)
 Gantt chart
 Milestone chart
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Project Scheduling
Tasks
Review
Start
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
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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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Essential Scheduling Data (Example)
Activities and Times
Activity
a
b
c
d
e
f
g
h
i
j
k
l
m
n
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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
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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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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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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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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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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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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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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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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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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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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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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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Forward Pass (continued)
Full precedence diagram
ES
1
EF
8
Duration=7
Task A
LS
LF
ES
8
EF
14
Duration=6
Task C
LS
LF
ES
14
EF
17
Duration=3
Task G
LS
LF
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
ES
7
Finish
LF
EF
10
Duration=3
Task E
LS
LF
Duration=2
Task F
LS
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Unit 10 | Network Logic and Scheduling
LF
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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
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Project Management
Backward Pass (continued)
Full precedence diagram
ES
1
EF
8
ES
8
EF
14
Duration=7
Task A
Duration=6
Task C
1
LS
8
LS
8
LF
14
LF
ES
14
EF
17
Duration=3
Task G
14
LS
17
LF
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
ES
7
Finish
19
LF
EF
10
Duration=3
Task E
14
LS
17
LF
Duration=2
Task F
12
LS
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LF
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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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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
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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
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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
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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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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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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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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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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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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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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
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8
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9
4
8
8
10
3
3
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© IBM Corporation 2003
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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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
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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
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9
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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 2003
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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© IBM Corporation 2003
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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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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© IBM Corporation 2003
Project Management
Sample Gantt Chart
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Unit 10 | Network Logic and Scheduling
© IBM Corporation 2003
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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February
March
April
May
June
© IBM Corporation 2003
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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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
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Unit 10 | Network Logic and Scheduling
© IBM Corporation 2003
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
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Unit 10 | Network Logic and Scheduling
F
© IBM Corporation 2003