Network techniques are in essence a modification of the age old Bar Chart techniques of controlling the various works in a project. The Bar Chart has certain drawbacks or difficulties i.e. it is not capable of depicting proper relationships in time between various jobs to be done in a project. Moreover, once the relationship in time of the different jobs in a project is shown in the form of a Bar-Chart, it is difficult to change these Charts. The Bar Charts are, therefore, somewhat ‘static’ in character. The network technique helps to overcome this difficulty. PERT and CPM network techniques allow the project planner, and implementer to show graphically the proper sequencing and relationships-in-time between different jobs in the project and to concurrently indicate the requirements of time, money, materials, manpower and other resources on the network chart itself.
We shall restrict here to a description of the Critical Path Method (CPM) in this article. Later, we shall introduce the related technique of PERT. But it needs to be reiterated here that both these techniques have much in common and they fall under the general category of network techniques.
Whether our purpose is to draw a network for CPM or to draw a bar chart, the basic requirement for both these graphical techniques is to analyze the various work components of the project and there from get a listing of the jobs to be performed in the project from the beginning to the end of the project. This would help us to proceed in systematic manner rather than listing the jobs in a haphazard manner. Such a systematic listing of jobs can only produce a systematic graphical representation of these jobs, their inert-relationship with one another with respect to time and their resources requirements.
The very word ‘job’ connotes that someone has been assigned the responsibility for a task and that the responsibility for the completion of that should also be clearly understood by the person who is responsible for the job. It also follows that unless the various jobs are planned by taking into account the responsibility and the authority to carry it out, the planning for the project becomes meaningless. Therefore, the organization of the project as whole becomes an extremely important starting point for the building up of a network.
The work of implementing the project can be broken down into certain major packages or work elements. This division of labor naturally, has to be done keeping in view the organization of the project. The organization of the project can be done in several ways depending upon various factors as mentioned below.
Geographic: A project may be carried out at two or three different locations so far removed that it becomes necessary to control these work components as individual units under the responsibility of the head of that unit. For instance, in a hydel project, it may be necessary to build two or three different dams at different locations. Because for the distance and the geographical separation of the locations it may become necessary to treat the work package at these different locations as comprising one aggregate individual unit.
Functional: The work in the project may of different kinds, for instance civil, electrical, mechanical, geological etc. These functional areas of the work need to be organized separately.
Product wise: Sometimes the work components in the project need to be grouped by means of the product such as the water conductor system, the dam, the irrigation channels etc. Such a grouping will simplify the organization of the project work in some cases.
Time-wise: The project can sometimes be divided into Phase-I, Phase- II, Phase III etc., based on the time phasing of the project. In each phasing a major chunk of the project work is done. In such a case, it may be necessary to organize the work of the project according to the time phasing.