Introduction to the software development process model

Compare the three common and basic software development process models: waterfall model, unified process model, and spiral model.

The waterfall model, the Unified Process Model of RUP, and the spiral model are both methods for software lifecycle management, and there is a certain relationship between them, however, the application environments and features of the three models are quite different.

For example, the waterfall model emphasizes stages of development, early planning and demand investigation, and product testing, however, the result is often that the original understanding of the requirements is wrong only after the system is delivered to the customer, and the problems in the system design can only be found at the test stage; the ability to control project risks is weak; software projects are often postponed or development costs exceed the budget, and the project development progress is often disrupted by unexpected problems, rework or other additional development cycles are required, resulting in project delays or overspending.

 

In addition, in the traditional waterfall model, problems in requirements and design cannot be detected in the early stage of project development. Only when the system is integrated for the first time, these design defects are exposed during testing, resulting in a series of rework: re-design, coding, and testing, resulting in project delays and increased development costs.

 

However, in early software development and many simple software development projects, waterfall development model applications are still common. This method can be used for some simple modules of a single department-level application software or a large application software with simple requirements and clear objectives, for example, this model can be used for simple office software applications or ERP module development of simple and single logistics, finance, and inventory software.

 

The Unified Process Model of RUP has many advantages over the waterfall model. It allows changes and optimization of system requirements first, and demonstrates some system functions generated by iteration to the business department, R & D personnel can collect feedback from business departments on the system as soon as possible, and correct deviations in understanding the requirements of business departments in a timely manner to ensure that the developed system truly solves their problems. Second, elements can be gradually integrated. In traditional project development, because all modules in the system need to be integrated at once, the integration phase usually accounts for a large proportion of the work of the entire project (up to 40% ), work at this stage is often uncertain and tricky.

 

In the Unified Process Model of RUP, integration can be said to be continuous. Each iteration will integrate some new system functions, but the elements to be integrated are much less than in the past, therefore, the workload and difficulty are relatively low. In addition, the Unified Process Model of RUP can help enterprises reduce software development risks as early as possible, increase IT team morale and generate higher quality products. Each iteration generates a runable system. By testing this runable system, enterprises can detect and correct defects in an early iteration, performance bottlenecks can also be discovered and processed as soon as possible. Because errors are always corrected in each iteration, enterprises can get higher quality products.

 

Therefore, it can be seen that the iterative model mainly solves risk control problems, and the system risks in the traditional development process need to reach the end of project development (mainly in the test phase) can be truly reduced. Risks in iterative development can be solved as early as possible through several iterations in the early stages of project development. Therefore, during the development of large-scale application software, enterprises should adopt iteration methods as much as possible, and divide the application software to be developed into several stages that can be completed, in order to reduce the risk of enterprise software development.

 

However, it should be pointed out that it is not safe to develop software for enterprise application iterative models. If strict process management is not required for iterative models, the life cycle model is likely to degrade to an original, unplanned "trial-error-change" model. In addition, due to constant adjustments and improvements, business departments are given early access to software functions that have not yet been tested and are well-developed, which has a negative impact on developers and business department personnel.

 

The basic practice of the spiral model is to introduce very strict risk identification, risk analysis and risk control before each development phase of the waterfall model. The development of the next stage is not planned until measures are taken to eliminate risks. It emphasizes strict risk management throughout the entire process and the quality of each development phase, and provides opportunities to review the value of the project to continue, but it introduces very strict risk identification, risk analysis and risk control put forward high requirements on the skill level of risk management, and require a large amount of talents, capital and time investment.