Constructing a network 1 Introduction and definitions: -Activity and Project -Project Management Process -Network 2 Situations in network diagram -Concurrent activities -Predecessors and Successors Activities -Dummy Activity 3 Errors to be Avoided in constructing a network 4 Rules in constructing a network

1. Faculty of Economics and Business Administration
Lebanese University
Chapter 5: Network analysis
Constructing a network
Dr. Kamel ATTAR
attar.kamel@gmail.com
F 2020 - 2021 F

2. 1
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
1 Introduction and definitions
Activity and Project
Project Management Process
Network
2 Situations in network diagram
Concurrent activities
Predecessors and Successors Activities
Dummy Activity
3 Errors to be Avoided in constructing a network
4 Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

3. 2
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Activity and Project
Project Management Process
Network
H Introduction and definitions H
Definition (Activity)
An activity represents an action and consumption of resources (men, machines,
materials, money, time and energy) required to complete a portion of a project.
Definition (Project)
A project is defined as a combination of interrelated activities which must be executed in
a certain order for its completion. We can say a project is defined by a set of activities.
• The projects may be extremely large and complex such as construction of a housing, a
highway, a shopping complex, maintenance, fabrication, purchasing, computer system
instantiation, research and development planning etc.
• It is required that managers must have a dynamic planning, scheduling and controlling
system with use of limited resources to produce the best possible results and also to react
immediately to the changing conditions and make necessary changes in the plan and
schedule.
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

4. 3
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Activity and Project
Project Management Process
Network
Definition (Project Management Process)
Network analysis is the general name given to certain specific techniques which can be used for
the planning, management and control of projects.
• Planning: planning involves setting the objectives of the project. Identifying various activities
to be performed and determining the requirement of resources.
• Scheduling: based on the time estimates, the start and finish times for each activity are
worked out by applying forward and backward pass techniques, critical path is identified,
along with the slack and float for the non-critical paths.
• Controlling: controlling refers to analyzing and evaluating the actual progress against the
plan. Reallocation of resources, crashing and review of projects with periodical reports are
carried out.
Network is a technique used for planning and scheduling of these large projects. There is multitude
of operations research situations that can be modeled and solved as network. Some recent
surveys reports that as much as 70% of the real-world mathematical programming problems can
be represented by network related models.
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

5. 4
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Activity and Project
Project Management Process
Network
Definition (Network)
It is a graphical representation of logical and sequentially connected activities and events of a
project. Network is also called arrow diagram.
Network analysis is known by many names
• PERT (Program Evaluation and Review Technique) developed during 1950’s. the technique
was developed and used in conjunction with the planning and designing of the Polaris missile
project.
• CPM (Critical Path Method), which was developed by DuPont company and applied first to
the construction projects in the chemical industry.
• PEP (Program Evaluation Procedure),
• LCES (Least Cost Estimating and Scheduling),
• SCANS (Scheduling and Control by Automated Network System), etc
We will present the two most widely applied algorithms PERT and CPM. These techniques are
used in project management to help the manager answer questions like:
• When will the project be finished?
• When is each individual part of the project scheduled start and finish?
• Which activities must be finished on time to avoid making the entire project late?
• Is it possible to shift resources to critical parts from other numerical parts without affecting the
overall completion time?
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

6. 5
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Concurrent activities
Predecessors and Successors Activities
Dummy Activity
H Situations in network diagram H
Each activity is represented by an arrow. An event (or node) will always occur at the beginning and
end of an activity. The event has no resources and is represented by a circle. The ith event and jth
event are the tail event and head event respectively.
Activities are usually classified into four categories:
• Concurrent activities: activities operate or occur at the same time
• Predecessors activities: activities that must be completed before the activity can start.
• Successors activities: activities can start when the activity complete.
• Dummy activities: it indicates only precedence relationships and does not require any time
of effort.
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

7. 6
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Concurrent activities
Predecessors and Successors Activities
Dummy Activity
Concurrent activities:
One or more activities can start and end simultaneously at an event
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

8. 7
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Concurrent activities
Predecessors and Successors Activities
Dummy Activity
Predecessors and Successors Activities:
Activities performed before given events are known as Predecessors activities
Activities performed after given events are known as Successors activities
• A must finish before either B or C can start.
• Both D and E must finish before F can start.
• Both A and B must finish before either of C or D can start.
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

9. 8
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Concurrent activities
Predecessors and Successors Activities
Dummy Activity
Dummy Activity: An imaginary activity which does not consume any resource
and time is called a dummy activity. Dummy activities are simply used to
represent a connection between events in order to maintain a logic in the
network. It is represented by a dotted line in a network.
• Both A must finish before either B or C can start.
• C must finish before D can start.
• C and B must finish before F can start.
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

10. 9
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
H Errors to be Avoided in constructing a network H
• Two activities starting from a tail event must not have a
same en event. To ensure this, it is absolutely necessary
to introduce a dummy activity, as shown in the figure
• Looping error should not be formed in a network, as it represents
performance of activities repeatedly in a cyclic manner, as show in the
figure.
• In a network, there should be only one start event and one
ending event.
The direction of arrows should flow from left to right avoiding mix-
ing of direction.
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

11. 10
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
H Rules in constructing a network H
• No single activity can be represented more than once in a network.
• The length of an arrow has no significance.
• The event numbered 1 is the start event and an event with highest number
is the end event. Before an activity can be undertaken, all activities
preceding it must be completed. That is, the activities must follow a logical
sequence (or-interrelationship) between activities.
• In assigning numbers to events, there should not be any duplication of
event numbers in a network.
• Dummy activities must be used only if it is necessary to reduce the
complexity of a network.
• A network should have only one start event and one end event.
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

12. 11
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Example (À)
Draw a network for a house construction project. The sequence of activities
with their predecessors are given in Table, below.
Name of Starting and Description of activity Predecessor Time duration
the activity finishing event (days)
A 1 → 2 Prepare the house plan – 4
B 2 → 3 Construct the house A 58
C 3 → 4 Fix the door/windows B 2
D 3 → 5 Wiring the house B 2
E 4 → 6 Paint the house C 1
F 5 → 6 Polish the doors/windows D 1
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

13. 12
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Name of Starting and Description of activity Predecessor Time duration
the activity finishing event (days)
A 1 → 2 Prepare the house plan – 4
B 2 → 3 Construct the house A 58
C 3 → 4 Fix the door/windows B 2
D 3 → 5 Wiring the house B 2
E 4 → 6 Paint the house C 1
F 5 → 6 Polish the doors/windows D 1
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

14. 12
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Name of Starting and Description of activity Predecessor Time duration
the activity finishing event (days)
A 1 → 2 Prepare the house plan – 4
B 2 → 3 Construct the house A 58
C 3 → 4 Fix the door/windows B 2
D 3 → 5 Wiring the house B 2
E 4 → 6 Paint the house C 1
F 5 → 6 Polish the doors/windows D 1
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

15. 12
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Name of Starting and Description of activity Predecessor Time duration
the activity finishing event (days)
A 1 → 2 Prepare the house plan – 4
B 2 → 3 Construct the house A 58
C 3 → 4 Fix the door/windows B 2
D 3 → 5 Wiring the house B 2
E 4 → 6 Paint the house C 1
F 5 → 6 Polish the doors/windows D 1
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

16. 12
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Name of Starting and Description of activity Predecessor Time duration
the activity finishing event (days)
A 1 → 2 Prepare the house plan – 4
B 2 → 3 Construct the house A 58
C 3 → 4 Fix the door/windows B 2
D 3 → 5 Wiring the house B 2
E 4 → 6 Paint the house C 1
F 5 → 6 Polish the doors/windows D 1
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

17. 12
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Name of Starting and Description of activity Predecessor Time duration
the activity finishing event (days)
A 1 → 2 Prepare the house plan – 4
B 2 → 3 Construct the house A 58
C 3 → 4 Fix the door/windows B 2
D 3 → 5 Wiring the house B 2
E 4 → 6 Paint the house C 1
F 5 → 6 Polish the doors/windows D 1
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

18. 12
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
The network diagram in Figure shows the procedure relationship between the activities.
• Activity A (Preparation of house plan), has a start event 1 as well as an ending event 2.
• Activity B (Construction of house), begins at event 2 and end at event 3.
The activity B cannot start until activity A has been completed.
• Activities C and D cannot begin until activity B has been completed, but they can be
performed simultaneously.
• Similarly, activities E and F can start only after completion of activities C and D respectively.
• Both activities E and F finish at the end of event 6.
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

19. 13
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Example (Á)
Draw a network for a house construction project. The sequence of activities
with their predecessors are given in Table, below.
Activity Description of activity Predecessor
A Purchase of land –
B Preparation of building plan –
C Level or clean the land A
D Register and get approval A,B
E Construct the building C
F Paint the building D
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

20. 14
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
The activities C and D have a common prodecessor A. The network representation shown in
Figure violates the rule that no two activities can begin and end at the same events. It appears as if
activity B is a predecessor of activity C, which is no the case.
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

21. 14
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
The activities C and D have a common prodecessor A. The network representation shown in
Figure violates the rule that no two activities can begin and end at the same events. It appears as if
activity B is a predecessor of activity C, which is no the case.
To construct the network in a logical order, it
is necessary to introduce a dummy activity as
shown in Figure.
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

22. 15
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Example (Â)
Construct a network for a project whose activities and their predecessor
relationship are given in Table, below.
Activity A B C D E F G H I J K
Predecessor - - - A B B C D E H, I F, G
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

23. 16
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Activity A B C D E F G H I J K
Predecessor - - - A B B C D E H, I F, G
The network diagram for the given problem is shown in Figure with activities A, B and C starting simultaneously.
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

24. 16
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Activity A B C D E F G H I J K
Predecessor - - - A B B C D E H, I F, G
The network diagram for the given problem is shown in Figure with activities A, B and C starting simultaneously.
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

25. 16
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Activity A B C D E F G H I J K
Predecessor - - - A B B C D E H, I F, G
The network diagram for the given problem is shown in Figure with activities A, B and C starting simultaneously.
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

26. 16
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Activity A B C D E F G H I J K
Predecessor - - - A B B C D E H, I F, G
The network diagram for the given problem is shown in Figure with activities A, B and C starting simultaneously.
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

27. 16
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Activity A B C D E F G H I J K
Predecessor - - - A B B C D E H, I F, G
The network diagram for the given problem is shown in Figure with activities A, B and C starting simultaneously.
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

28. 16
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Activity A B C D E F G H I J K
Predecessor - - - A B B C D E H, I F, G
The network diagram for the given problem is shown in Figure with activities A, B and C starting simultaneously.
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

29. 17
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Example (Ã)
Draw a network diagram for a project given in Table, below.
Activity A B C D E F G H I J K L
Predecessor - A B A D C E D D H H F, H G, J
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

30. 18
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Activity A B C D E F G H I J K L
Predecessor - A B A D C E D D H H F, H G, J
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

31. 18
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Activity A B C D E F G H I J K L
Predecessor - A B A D C E D D H H F, H G, J
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

32. 18
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Activity A B C D E F G H I J K L
Predecessor - A B A D C E D D H H F, H G, J
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

33. 18
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Activity A B C D E F G H I J K L
Predecessor - A B A D C E D D H H F, H G, J
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

34. 18
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Activity A B C D E F G H I J K L
Predecessor - A B A D C E D D H H F, H G, J
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

35. 18
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Activity A B C D E F G H I J K L
Predecessor - A B A D C E D D H H F, H G, J
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

36. 18
Introduction and definitions
Situations in network diagram
Errors to be Avoided in constructing a network
Rules in constructing a network
Example 1
Example 2
Example 3
Example 4
Solution
Activity A B C D E F G H I J K L
Predecessor - A B A D C E D D H H F, H G, J
Dr. Kamel ATTAR | Chapter 5: Network analysis | Constructing a network

37. Thank you! Questions?