What does the logical relationship of the network include?
In other words, network planning technology refers to the management technology used for the planning and control of engineering projects. It was developed in the late 1950s. According to its origin, it can be divided into critical path method (CPM) and plan review method (PERT).
CPM is mainly used for contracted projects that have gained some experience in similar projects in the past, while PERT is more used for R&D projects.
Network planning method originated in the United States and is an important method of project planning management. Starting from 1956, some mathematicians and engineers in the United States began to discuss this problem.
1957, DuPont chemical company of America adopted a new plan management method, namely critical path method (CPM) for the first time. In the first year, it saved more than1million dollars, equivalent to more than five times of the company's research and development CPM expenditure.
1958, when developing Polaris missile submarine, the Special Planning Office of the US Naval Weapons Bureau applied a planning method called PERT, which made Polaris missile submarine completed two years ahead of schedule.
Statistics show that PERT can advance the schedule by 15%-20% and save costs by 10%- 15% without increasing manpower, material resources and financial resources. Network planning method has been widely used in the management of various large-scale engineering projects in China.
CPM and PERT are independent development planning methods, and there are differences in specific practices. CPM assumes that the time of each activity is certain, while PERT's activity time is based on probability estimation. CPM not only considers the activity time, but also considers the activity cost and the balance between cost and time, while PERT pays less attention to cost.
CPM adopts node network diagram and PERT adopts arrow network diagram. But the basic principles of the two are basically the same, that is, expressing the logical relationship of specific activities in a project plan through network form, which is now collectively called network planning technology.