Spm ap-network model-

Activity Planning Network Model

1. SPM-UNIT II
ACTIVITY PLANNING
Prof. Kanchana Devi

2. Network Planning Models
Prof. Kanchana Devi
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Scheduling techniques model the project’s activ ities and
their relationships as a “Network”.
In network time flows from left to right
These techniques were developed in 1950’s
There are two best techniques:
CPM (Critical Path Method)
PERT (Program Evaluation Review Technique)
Both uses an “activity-on-arrow” approach
Activities are drawn as arrows joining circles, or nodes
Which show the start and completion time of the activities

3. Precedence Network
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Recently used , Popular one
It uses “activity-on-node” networks
Where activities are represented as nodes
Links between the nodes are represented as
sequencing requirements.

4. Formulating a Network Model
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First stage:
Representing the activities and their
relationships as graph.
In “Activity-on-node”
Representing the activities as nodes(boxes) and
the lines between nodes represent the
dependencies.

5. Rules: Constructing Precedence
Network
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A project network should have only one start
node
A project network should have only one end
node
A node has a duration
Links normally have no duration
Precedents are the immediate preceding
activities
Time moves from left to right
A network may not contain loops
A network should not contain dangles

6. Fragment of precedence Network
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Install
Program
Test
Data
Take-on
Code

7. A loop represents an impossible
sequence
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Code
Program
Release
Program
Test
Program
Diagnose
Errors
Correct
Errors

8. A Dangle
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Design
Program
Install
Program
Test Program
Code
Program
Write User
Manual

9. Resolving the Dangle
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Design
Program
Install
Program
Test
Program
Code
Program
Write
User
Manual
Sign-Off

10. Representing Lagged Activities
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Undertake two activities in parallel as there
is a lag between two.
Activities are lagged because a stage in one
activity must be completed before the other
may proceed.
Show each stage as separate activity.

11. Adding Time Dimension
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Each activity have an estimate of its duration.
Forward pass – Earliest dates at which
activities may commence and project be
completed.
Backward pass – Latest start dates for
activities and critical path.

12. Project Specification
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13. Project Activity Network
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14. Project Activity Network
represented as CPM Network
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15. Dummy activities
15
When two paths within a network have a
common event to occur.
It is incorrect to require both hardware
specification and data structure design

16. Using Dummy Activities
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17. …….
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Dummy activities shown as dotted lines have
a zero duration and use no resources.

Use of dummy activity where two activities
share the same start and end nodes makes it
easier to distinguish activity end points.

18. Forward Pass
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Activity Duration
(Weeks)
Earliest Start
Date (Weeks)
Earliest Finish
Date(Weeks)
A 6 0 6
B 4 0 4
C 3 6 9
D 4 4 8
E 3 4 7
F 10 0 10
G 3 10 13
H 2 9 11

19. CPM Network
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20. A CPM Network after forward
pass
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21. Activity table for forward pass
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Activity Duration
(weeks)
Earliest
Start
Date
Latest
Start
Date
Earliest
Finish
Date
Latest
Finish
Date
Total
Float
A 6 0 6
B 4 0 4
C 3 6 9
D 4 4 8
E 3 4 7
F 10 0 10
G 3 10 13
H 2 9 11

22. Backward Pass
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23. CPM Network after the backward
pass
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24. Identifying the Critical Path
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Any delay on the critical path will delay the
project.
Difference between earliest and latest date
for an event is known as slack.
Event with slack of zero is critical as any
delay in achieving that event will delay the
completion date of the project.

25. Critical Path
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Event
Number
Latest
Date
Earliest
Date
Slack

26. Activity Float
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As events have slack, activities possess float.

Total float is the difference between earliest
start and latest start ( or difference between
earliest finish and latest finish)

27. Activity Schedule showing total
float for each activity
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28. Activity Schedule
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Actvity Name Time Actvity Name Time
1-2 A 4 5-6 G 4
1-3 B 1 5-7 H 8
2-4 C 1 6-8 I 1
3-4 D 1 7-8 J 2
3-5 E 6 8-10 K 5
4-9 F 5 9-10 L 7

29. Activity Network Diagram
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1
2
3
5
4
7
6
8
10
9

30. Solution
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Activity Activity
Name
Normal
Time
E.S E.F L.S L.F Total
Float
1-2 A 4 0 4 5 9 5
1-3 B 1 0 1 0 1 0
2-4 C 1 4 5 9 10 5
3-4 D 1 1 2 9 10 8
3-5 E 6 1 7 1 7 0
4-9 F 5 5 10 10 15 5
5-6 G 4 7 11 12 16 5
5-7 H 8 7 15 7 15 0
6-8 I 1 11 12 16 17 5
7-8 J 2 15 17 15 17 0
8-10 K 5 17 22 17 22 0
9-10 L 7 10 17 15 22 5

31. Problem 1
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Draw activity network of the project.
Find total float of each activity.

Activity Time in Weeks
1-2 20
1-3 25
2-3 10
2-4 12
3-4 5
3-5 10

32. Problem 2
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Find out the critical path and total float.
Activity Immediate
Predecessor
Time
A 3
B 8
C 5
D A 9
E C 2
F B,E 6
H B,E 12
G D 11