Five common development models

The following is an analysis of several development models, combined with theories.
    1. Iterative model
    The iterative model abandons the traditional process of requirements analysis, design, coding, and testing, but turns the entire life cycle into several sprint (Sprint) stages, and each stage is composed of several or all of the above traditional The composition of the process, in each stage, will include the following four stages: initial stage, refinement stage, construction stage, delivery stage. In the initial phase, confirm the sprint scope, boundaries, system selected architecture, plan, and required resources. In the elaboration phase, the problem is scoping, development cases are created, templates are created, and tools are prepared. The main tasks in the build phase are to complete the development and testing of the build, integrate the completed build into a product, and test all functionality (CI). In the delivery phase, the sprint is mainly completed and the software product is delivered to the relevant stakeholders.


    2. Spiral model
    Spiral model, with particular emphasis on the risk analysis stage, is especially suitable for large and complex, very high-risk projects. Typically the spiral model consists of four stages: planning, risk analysis, implementation engineering, and customer assessment. In the spiral model, the first model released may not even have any output, and may only be a goal on paper, but with repeated deliveries, each version will move towards a fixed goal and eventually get a more Complete version.


    3. Prototyping
    model The first step in the prototyping model is to create a rapid prototype, which can meet the needs of project stakeholders and future users to interact with the prototype, and then fully discuss and analyze with relevant stakeholders to finally figure out the current system. After a full understanding of the needs of the company, a product that is satisfactory to the user is developed on the basis of the prototype. In the actual project process, with the help of organizational process assets and rapid model software, some simple prototypes can generally be established during requirements analysis. For example, in the first YH company, because it is an "industry software provider", Therefore, with industry solution software solutions in various regions, the usual trick is to take projects from other cities to the implementation site of this project as a prototype model. Prototyping models are meaningful project practices.


    4.V model
    The V model as a whole looks like a V-shaped structure, consisting of left and right sides. The underlines on the left represent requirements analysis, outline design, detailed design, and coding, respectively. The overlines on the right represent unit tests, integration tests, system tests, and acceptance tests. It seems that the V model is a symmetrical structure, and its significance lies in that it clearly shows the different levels that exist in the testing process, and clearly describes the corresponding relationship between these testing stages and development stages.


    5. Waterfall model
    The waterfall model is a very classic, even a bit old-fashioned cycle model. Generally, it is divided into several stages such as planning, requirements analysis, outline design, detailed design, coding, unit testing, testing, operation and maintenance, etc. . The cycles of the waterfall model are interlinked. The interaction point in each cycle is a milestone. At the end of the previous cycle, the work result of this activity needs to be output, and the work result of this activity will be used as the input of the next cycle. In this way, when an uncontrollable problem occurs in a certain stage, it will lead to rework, return to the previous stage, or even delay the next stage.