Three-layer, multi-layer structure just like individuals, are responsible for their different work. Know they know, they should know that they do not know.
Do not gossip, do not ask yourself should know.
Presentation Layer:
should not know: should not see the physical data storage. There should be no connection strings, Connections, Commands, or similar.
You should know: should know the main module.
Business logic layer:
should not know: should not know where in the database. There should be no connection strings, Connections, Commands, or similar.
You should know: should know the business logic, business processes
Data Access Layer:
should not know: should not know HTML, asp.net, know the business logic of the things to avoid as well as what kind of database use.
Should know: you should know how to access the data storage layer, such as Create, Read, Update, Delete, etc.
Data storage layer:
should not know: should not know HTML, asp.net. You should not know that language is used, Chinese or English.
You should be aware of: storing structured data, connection strings, Connections, Commands, etc.
I do not know how we are layered?
Reproduced in: https: //www.cnblogs.com/martinxj/archive/2004/07/16/24979.html