What Is a Network Model?

Computer network refers to an aggregate of many autonomously working computers connected by communication lines. What rules are used for communication between various components is a problem of network model research. The network model generally refers to the OSI seven-layer reference model and the TCP / IP four-layer reference model. These two models are most widely used in networks.

The original inventor of the network model was

Some notable database systems that use network models include:

• Integrated Data Storage (IDS)

• Figure 3 OSI seven-layer reference model

  1. Network model with material flow

  When the flow content in the network model is a material entity such as liquid, gas, or solid, it constitutes a network model that uses matter as the flow. The optimization goal is generally the maximum flow or the minimum cost flow. Many practical problems such as transportation (road, railway, aviation, navigation), resource allocation, and industrial process devices can be abstracted into this type of network model.

  In the example in Figure 4-1, if the digital well along the line is not a distance, but the maximum flow that the corresponding highway can pass, it becomes a network model with material as the flow.

  2. Information-based network model

  Examples of network models that use signals, data, and other information as traffic, in addition to broadcast and communication networks, include block diagrams or flow diagrams used in the control process, social organization system diagrams, and management information system networks.

  Figure 4-2 shows the control system diagram of construction enterprise operation forecast. The enterprise must first determine the forecast goals and requirements according to the actual needs of production and operation, collect relevant data accordingly, select a suitable forecast method for forecasting, and then analyze whether the forecast conclusion is reasonable, if it is not reasonable, or revise the pre-donation 0 target and If required, or re-select the forecasting method, on the other hand, you can enter the forecasting implementation and use the forecasting conclusions to guide the production and operation activities of the enterprise. During the implementation, you may encounter new production and management forecasting problems and start a new cycle.

  3 Network model with energy as traffic

  The most typical network systems that use energy as the flow are urban power systems and central heating systems. Figure 4-3 shows a schematic diagram of a city's power network.

  Figure 4 Network model

  4 Network model with time, cost, distance, etc. as traffic

  The network model that takes time as the flow is the most typical PERT (Plan Review Technology). Figure 4 · 4 is a network diagram showing the construction order of prefabricated houses. In the figure, each arrow line indicates a job and indicates the estimated number of working hours. Using this network diagram, it is possible to find out the optimal scheme in the entire construction process, to reasonably solve problems such as labor arrangements, capital turnover, and shortening of construction periods. The shortest possible time in this example is 66h.

  Figure 4-5 shows the plan decision tree with costs as the expected value. It describes the problem: a construction company is constructing a project in a riverside depression, and the project site has been affected by the rising river in the past. Destructive flooding has also been encountered. Since the project does not use equipment for four months, a storage plan for the equipment needs to be determined. There are three options to choose from: one is to remove the equipment and return it when needed, which will cost a total of 1,800 yuan; the other is to leave the equipment on the construction site and build a platform to protect it. The cost of building the platform is 500 yuan. This platform can defend against large waters, but cannot prevent destructive flooding. Third, the equipment is left on the construction site without protection measures ^[3] .

  Figure 5 Network model