对此可能还有其他流派，但对我来说，如下：

There are probably other schools of thought on this, but for me it's as follows:

模型与应用程序紧密耦合，直接引用数据库模式/体系结构/文件路径等。

Models are tightly coupled to your application, making direct references to your DB schema/architecture/file paths etc.

图书馆是松散耦合的。它们应被视为第三方添加物，并且不应对您的应用或系统做任何假设。您应该能够以最少的配置随意插入库。确实，事实恰恰相反，您的库文件夹中的项目应该能够放入任何其他CI应用程序中。

Libraries are loosely coupled. They should be treated like 3rd party add-ons and should make no assumptions about your app or your system. You should be able to "drop in" libraries at will with a minimum amount of configuration. Indeed, the opposite should be true, items in your library folder should be able to be dropped into any other CI application.