Based on the principles of informat

Based on the principles of information systems, the system architecture model can be divided into three layers: user interface layer, business layer, and data access layer, as shown in Figure 4-6. 1. Data access layer: It is mainly the operation layer for the original data (database or text file and other forms of storing data), not the original data, that is to say, it is the operation of the data, not the database, specifically the business logic The layer or presentation layer provides data services. 2. Business logic layer: It is mainly for the operation of specific problems. It can also be understood as the operation of the data layer and the processing of data business logic. If the data layer is building blocks, then the logic layer is the construction of these building blocks. 3. Presentation layer: It mainly represents WEB mode, and can also be represented as WINFORM mode. If the logic layer is quite powerful and complete, no matter how the presentation layer is defined and changed, the logic layer will provide perfect services.