Layered Web Applications with ASP.NET

In the diagram in figure 1 you see a process go around in a counter clockwise direction. The process goes through the following 6 steps:

1. The Presentation layer asks the BLL for some object, for example a contact person.


2. The BLL can optionally perform some validation (for example, is the current user allowed to make this call?) and then forwards the request to the DAL.


3. The DAL connects to the database and asks it for a specific record.


4. When the record is found, it is returned from the database to the DAL.


5. The DAL wraps the database data in a custom object and returns it to the BLL.


6. Finally, the BLL returns the object to the Presentation layer, where it could be displayed on a web page for example.