The document discusses rules for constructing network diagrams that represent project operations. Some key rules include: arrows represent activities and circles represent events; networks flow from left to right with activities only starting once all preceding activities are complete; each activity must start and end at a circle; event numbers increase from tail to head; networks can only have one initial and one terminal node; dummy and parallel activities are not permitted; and looping or burst events are also not allowed.

1. Subject: Operations Research
Topic: Rules for Network Construction
By
A. Raja

2. Network Diagram
• A Network is a graphic representation of a project’s
operations and is composed of activities and events
that must be completed to reach the end objective of a
project.
• A Project network consists of a number of nodes
(shown as small circles or rectangles) and a number of
arcs(shown as arrows) that connect two different
nodes.

3. Rules of Network Construction
• In Network diagram, arrows represent activities
and circles the events. The length of an arrow is of
no significance.
Event Event
Activity
• Network Diagrams flow from left to right.
• An activity cannot begin until all preceding
connected activities has been completed.

4. • Each activity should be represented by only one
arrow and must start and end in a circle.
• The tail of an activity represents the start and head
the completion of work.
• Events are identified by numbers.
•A network should have only one initial and one
terminal node.
Tail Head
6
5
4
4
3
2
1
Initial Terminal

5. • The general rule for numbering the event is that
the head event should always be numbered larger
than that at its tail.
• An event number should not get repeated or
duplicated.
• A dummy activity does not consume either any
resource of time.
• Parallel activities can not accepted between the
events.
1 2

6. • Looping is not permitted in a network. Thus , if A
precedes B, and B precedes C , then C cannot
precede A.
A
BC
BA C

7. • The initiation of more than one activity is called
the burst event.
• An Event which represents the join completion of
more than one activity is known as a merge event

8. Thank you