Network Diagram Representation
In a network representation of a project few definitions are used
Any individual operation which makes use of resources and has an end and a starting is called as activity. An arrow is generally used to characterize an activity with its head representing the direction of progress in the project. These are divided into four classes
The dummy activity is included in the network to clear the activity pattern in the next two situations
For instance, take a situation where A and B are concurrent activities. C is reliant on A and D is reliant on A and B both. This type of situation can be handled with the use of dummy activity as shown in the figure.
An event signifies a point in time representing the completion of several activities and the starting of new ones. This is typically symbolizes by a circle in a network which is also known as node or connector.
The events are divided into three categories
The first requirement in the development of network is to keep the precedence relationships. In order to prepare a network, the subsequent points must be taken into considerations
As all further calculations are on the basis of network, it is essential that a network be drawn with full care.
Rules for Drawing Network Diagram
Each of the activity is symbolized by one and only one arrow in the network
No two activities can be recognized by the same end events
To assure the correct precedence relationship in the arrow diagram, various questions must be tested every time any activity is added to the network
In case of big network, it is necessary that certain good habits be applied to draw an easy to follow network
Common Errors in Drawing Networks
The three types of errors are most frequently seen in drawing network diagrams
To cut off an activity prior to the completion of all activities in a network diagram is referred to as dangling. As reveal in the figure activities (5 - 10) and (6 - 7) are not the final activities in the network. So the diagram is incorrect and shows the error of dangling
2. Looping or Cycling
Looping error is also called as cycling error in a network diagram. Making an endless loop in a network is called as error of looping as revealed in the following figure.
Needlessly put the dummy activity in network logic is called as the error of redundancy as reveal in the diagram below
Advantages and Disadvantages
PERT/CPM has the subsequent advantages
PERT/CPM has the subsequent disadvantages:
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