● Cost modeling technology
According to the characteristics of the project, the project cost is predicted by mathematical model. Generally, historical cost information (related to some software measures of project cost) is used to establish an estimation model, through which workload and cost are predicted.
● Expert judgment technology
Also known as Delphi method, one or more domain experts and software development technicians are hired to estimate the project cost respectively, and finally an agreement is reached to get the final cost.
● Analogy evaluation technology
According to the actual cost of similar projects in the past, this project is estimated.
● Parkson rule
Parkson's law shows that work can be reflected by the required time. In software cost estimation, this means that the cost is determined by available resources, not by objective evaluation. If a software needs five people to complete in 12 months, then the workload is 12×5 = 60 person-months (PM).
● Top-down estimation method
Cost estimation mainly depends on the work breakdown structure, product function and sub-function composition form to realize the function and share the cost layer by layer.
● Bottom-up estimation method
Firstly, the cost of each component unit is estimated, and then the final cost estimate is obtained by accumulating according to the work breakdown structure.
● Profit pricing method
The cost of software is calculated by estimating the investment that users are willing to invest in the project. The budget of expenses depends on the customer's budget rather than the function of the software.
These estimation methods all have their advantages and disadvantages, and it is impossible to simply evaluate a certain method and its advantages and disadvantages. In large IT projects, it is usually necessary to adopt several estimation methods at the same time and compare their estimation results. If the estimation results of different methods are quite different, it means that we have not collected enough cost information, so we should continue to try to obtain more cost information and re-estimate the cost until the estimation results of several methods are basically the same.
Cost budget is a decomposition process after determining the overall cost. Decomposition mainly includes two aspects: First, cost allocation is carried out according to the work breakdown structure and work tasks (work packages), so that the costs of each work can be compared with each other, and when there is deviation, which work is out of order can be determined; The second is to allocate the cost according to the time period of the project, and allocate the budget cost to each time period of the project, so as to determine the accumulated cost that should be spent in a certain time period in the future, check the deviation and evaluate the cost performance.
At present, there are three most commonly used and best measurement methods: scale-oriented (LOC), function point-oriented (FP) and COCOMO model.