为什么要分层？

在计算机科学和信息技术的领域，分层是一种重要的设计和架构模式。分层是将系统或组件分为不同的层级，每个层级都有其特定的功能和职责。这种分层结构可以提高系统的可维护性、可扩展性和灵活性。

那么，为什么我们要分层呢？首先，分层可以帮助我们将复杂的问题分解为更小的、更易于处理的部分。每个层级都有其特定的功能，这样我们就可以更加专注于解决特定的问题，而不是将所有的问题混在一起。这可以使我们更高效地开发和维护系统。

其次，分层可以提高系统的可扩展性和灵活性。由于每个层级都是独立的，因此当我们需要添加新的功能或修改现有的功能时，只需要修改特定层级的代码，而不会影响到其他层级。这可以大大降低系统维护的开销，并提高系统的可扩展性。

此外，分层也有助于提高系统的安全性。每个层级都有其特定的权限和职责，因此通过限制每个层级的访问权限，我们可以更好地保护系统中的敏感信息。同时，通过分离不同的职责，也可以降低系统的风险，避免由于某个层级的问题而影响到整个系统的稳定性。

总之，分层是一种有效的设计和架构模式，可以帮助我们更好地理解和设计系统。通过将系统划分为不同的层级，我们可以提高系统的可维护性、可扩展性和灵活性，同时也可以提高系统的安全性和稳定性。英文翻译对照：
Why Layered Design?

In the field of computer science and information technology, layered design is an important pattern of design and architecture. Layered design refers to the division of a system or components into different layers, each layer having specific functions and responsibilities. This layered structure can improve the maintainability, scalability, and flexibility of the system.

So, why do we need layering? Firstly, layering can help us decompose complex problems into smaller and easier to handle parts. Each layer has its specific function, so we can focus more on solving specific problems rather than mixing all the problems together. This can make us more efficient in developing and maintaining systems.

Secondly, layering can improve the scalability and flexibility of the system. As each layer is independent, when we need to add new functions or modify existing functions, we only need to modify the code of specific layers without affecting other layers. This can greatly reduce the maintenance cost of the system and improve its scalability.

In addition, layering can also help improve the security of the system. Each layer has its specific permissions and responsibilities, so by limiting the access permissions of each layer, we can better protect sensitive information in the system. At the same time, by separating different responsibilities, we can also reduce the risk of the system and avoid affecting the stability of the entire system due to problems in a specific layer.

In conclusion, layered design is an effective pattern of design and architecture that can help us better understand and design systems. By dividing systems into different layers, we can improve their maintainability, scalability, and flexibility, while also improving their security and stability.