The following technical terms need to be clearly understood before building a CPM network:

1. activity

An activity is a part of a project on the network denoted by an arrow. The tail of the arrow indicates the start of the activity while the head indicates the end of the activity. One and only one arrow is used to represent an activity of a given period. The arrows of activities are not drawn to scale. The duration of the activities is written with their arrows.

2. dummy activity

The activity which neither uses any resource nor any time to complete it is called dummy activity. This is indicated by a dotted arrow or a solid arrow with a zero time period.

3. events

Event is the stage or point where all previous tasks are merged into it and finished tasks are still to be completed. Event 1 is the starting point of the project.

See the figure shown below, where event 6 is the point where activities B(3), F(3), H(2) and K(5) merge and activity L(4) bursts.

Advantages of PERT and CPM Methods

Events are usually represented by circles or nodes at the junction of arrows. The events are numbered chronologically in their chronological order.

4. Network

The graphical representation of the activities of the entire project is called a network of flow diagrams. The various tasks of the project are shown on this diagram in the order in which they are required to be performed.

5. Early Start Time (EST)

The earliest possible time at which an activity can start is called the initial start time.

6. Early Finish Time (EFT)

The sum of the initial start time of an activity and the time taken for its completion is called early end time.

7. Late Start Time (LST)

The latest possible time at which an activity can start without delaying the project date is called late start time.

8. Late Finish Time (LFT)

The sum of the late start time of an activity and the time taken for its completion is called late end time.

9. Everywhere

The difference between the maximum time allowed for an activity and its estimated duration is called the total float. It is the period of time by which the activity can be started late, without disrupting the project’s schedule. It is usually represented by s,

10. free swim

The period of time by which the completion time of an activity can be delayed without affecting the start of successful activities is called free float. It is usually represented by sf,

1 1 important activities

The event in which there is no float is called critical activity. Important events need to be completed on time.

12. risky way

The path in the network that is involved in critical events is called the critical path of action.

Er. Mukesh Kumar

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Er. Mukesh Kumar is Editor in Chief and Co-Funder at ProCivilEngineer.com Civil Engineering Website. Mukesh Kumar is a Bachelor in Civil Engineering From MIT. He has work experience in Highway Construction, Bridge Construction, Railway Steel Girder work, Under box culvert construction, Retaining wall construction. He was a lecturer in a Engineering college for more than 6 years.