Page 239 - DCOM303_DMGT504_OPERATION_RESEARCH

Operations Research

Notes Preceding and Succeeding Activities

Activities performed before given events are known as preceding activities (Figure 12.4), and
activities performed after a given event are known as succeeding activities.

Figure 12.4: Preceding and Succeeding Activities

A C
i j l

B
D
k

Activities A and B precede activities C and D respectively.

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, see Figure 12.5.

Figure 12.5: Dummy Activity

A B
Dummy
C

Errors to be avoided in Constructing a Network

1. Two activities starting from a tail event must not have a same end event. To ensure this, it
is absolutely necessary to introduce a dummy activity, as seen in Figure 12.6.
Figure 12.6: Correct and Incorrect Activities

3

Dummy

1 2

Incorrect Correct

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