Activity in Network Diagram Analysis & Use of Dummy Activity

Activity, use of dummy activity in the network diagram analysis

Activity in Network Diagram Analysis & Use of dummy activity:

Any individual operation, which utilizes resources and has a beginning and an end, is called an activity. It is represented by an arrow to depict an activity with its head indicating the direction of progress in the project. It is of four types:

(a) Predecessor Activity:

Activity that must be completed immediately prior to the start of another activity, is called predecessor activity.

(b) Successor Activity:

Activities that cannot be started until one or more other activities are completed but immediately succeed are called successor activities.

(c) Concurrent Activity:

Concurrent activity is defined as any activity that can be completed at the same time (concurrently). An action can come before or after an event, or it can happen at the same time as one or more of the other activities.

(d) Dummy Activity:

A dummy activity is one that does not consume any resources and merely represents technological dependence. It only indicates precedence relationships and requires no time or effort to use.

In the following scenarios, a dummy activity is inserted into a network to classify the activity pattern:

To distinguish activities with similar starting and ending points.
Identifying and maintaining the proper precedence relationship between activities that are not linked by events.

For example, consider the following situation for use of dummy activity in the network diagram analysis:

A and B are concurrent activities, D is dependent on B, and C is dependent on both A and B. A dummy activity can be used to deal with such a situation.

When two or more activities would start at the same node (event) and finish at the same node, i.e. they are exactly parallel. Then, between the end of one of the activities and the common finishing node, a dummy would be inserted.

This ensures that each activity has its own description when referred to by its start and finish node numbers. Dummies are frequently used to improve network layout. When they are not strictly required to represent the logic at hand. This is common at the beginning or end of a network, where a number of activities either start from or converge to a specific point.

(Source – Various books of college library)

Tags: use of dummy activity in the network diagram analysis, activity in the network diagram

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