Summarize the frequently seen system development cycle model.
In the past few years, it has been amazing to encounter a very clear requirement similar to the "entrepreneurial project library", the workload is very controllable, the quality requirements are relatively low, and business modeling is relatively easy, features constitute a relatively small "face project ". Similar to this type of project, it is very suitable to adopt the waterfall model in the traditional sense. If range control and risk control are better, it is really like a waterfall, the project will be delivered directly to the customer's small machine for deployment and operation, and everyone will enjoy the performance bonus and go home happily.
However, projects that only focus on "face" are difficult to deal with several times. On the other hand, even "face-oriented" projects should also attach great importance to quality links. Several elements of Project Management: quality, cost, time, and scope. Quality is the most important part of the project. If the quality is lost, it can be said that the project product has become a tree without roots, and the castle in the air. Therefore, it is very important to strengthen quality control and control the quality of each stage. Therefore, the V model is a symmetric structure that maps the development and verification processes.
In project practice, user requirements are always clearer as the project progresses, and it is very important to control user requirements. In order for users to have a clear understanding of their needs at the beginning of the project, prototype becomes very important, we often see in the Development of LOW-FI page prototype, other similar project demo even this type, users have a visual understanding of the future products. Analysis and Development Based on this will reduce many possible risks in subsequent processes. In the waterfall model and the V model, prototype is used in the demand analysis phase, which is very effective and even necessary.
Today, software projects are getting bigger and bigger, and the same project may be composed of several subsystems that interact with each other. In this way, the development of one or more models alone cannot meet the project's requirements for many aspects, as a result, the spiral model is derived. The reason why the spiral model is suitable for large-scale software is that it pays more attention to risk control, and emphasizes risk identification, risk analysis, and risk elimination.
In the next few years of work, we often develop based on the sprint cycle. This agile method is an implementation of iterative development. The so-called iterative model is to execute a traditional and complete serial process in every small stage of the project. execution once is an iteration, each iteration may contain all or part of the activities such as requirement analysis, design, coding, and testing.
This gives a brief understanding of the four development models of the software: waterfall model, V model, prototype model, spiral model, and iterative model.
Next we will analyze several development models one by one based on theory.
1. iterative model
Instead of traditional requirement analysis, design, coding, and testing processes, the iterative model converts the entire lifecycle into several sprint stages, each stage is composed of several or all of the above traditional processes. Each stage contains the following four stages: initial stage, refinement stage, construction stage, and delivery stage. In the initial phase, confirm the scope, boundaries, architecture, plan, and required resources of the sprint. In the Refinement phase, you can create domains for issues, create development cases, create templates, and prepare tools. The main task in the build phase is to complete the build development and test, integrate the completed build into a product, and test all the functions (CI ). In the delivery phase, the main task is to complete this sprint and deliver the software products to relevant stakeholders.
2. Spiral Model
The spiral model, especially in the risk analysis stage, is especially suitable for large, complex, and very high-risk projects. Generally, a spiral model consists of four stages: planning, risk analysis, implementation engineering, and customer evaluation. In a spiral model, the first model to be released may not even have any output, but may only be a goal on paper. However, with repeated delivery, each version will move towards a fixed goal, finally, a more complete version is obtained.
3. Prototype Model
The first step of the prototype model is to create a rapid prototype that allows stakeholders and future users to interact with the prototype, and then fully discuss and analyze the prototype with relevant stakeholders, finally, after fully understanding the requirements of the current system, a product that is satisfactory to the user is developed based on the prototype. In the actual project process, with the help of assets in the organizational process and quick model software, some simple prototypes can be established during demand analysis. For example, in the first YH company, because it is an "industry software provider", it has industry solutions in various regions. The usual trick is to take projects in other cities to the implementation location of this project as a prototype model. Prototype Model is a meaningful project practice.
4. V model
The V model looks like a v‑type structure, which consists of the left and right sides. The underline on the left represents the requirement analysis, outline design, detailed design, and encoding. The dashes on the right represent unit test, integration test, system test, and acceptance test. It seems that the V model is a symmetric structure, and its significance is that it clearly shows the different levels in the test process, the relationships between these test phases and development phases are clearly described.
5. Waterfall Model
The waterfall model is a classic or even a somewhat old cycle model, generally, it is divided into several stages, including planning, requirement analysis, outline design, detailed design, coding, Unit Testing, testing, and operation and maintenance. The cycle of the waterfall model is interlocking. The interaction point in each cycle is a milestone. The result of this activity must be output at the end of the previous cycle. The result of this activity will be input for the next cycle. In this way, when an uncontrollable problem occurs in a stage, it may lead to rework, return to the previous stage, or even delay the next stage.
Five typical development cycle models (waterfall, V, prototype, spiral, and iteration)
