注意的是大多数资源在构建时都会遵循一些自定义的协议，Note that resources are almost always constructed following some custom agreement.
Best practice is that such agreements make all knowledge about the content
of the resource explicit; if custom agreements do this, and declare their extensions
as required, then it is not necessary to understand the agreement when processing the
resource content.(这大段在说什么)
注意的是大多数资源在构建时都会遵循一些自定义的协议，Note that resources are almost always constructed following some custom agreement. Best practice is that such agreements make all knowledge about the content of the resource explicit; if custom agreements do this, and declare their extensions as required, then it is not necessary to understand the agreement when processing the resource content.(这大段在说什么)