Dummies are used to serve two purposes:

a. Grammatical purpose

b. Logical purpose.

a. Grammatical purpose: In a project, a situation may arise that two activities have the same beginning and end points. Such situations leads to a lot of inconvenience as the identity of the activities are lot. This results in errors during network computations. This problem can be solved by using a dummy, two activities cannot have the same starting and end event.

b. Logical purpose: Dummies are also used to clearly represent the logic of the network, where an activity is common to two sets of operations running parallel to each other. Hence for the activities having same name or function which is against the network rules. This situation can be overcome by the use of dummies.