Each database application is divided into three distinct components.
These components are as follows:
* Database services
This is the back-end database server and the data that resides in the database.
* Application services
This is the application or business logic that manipulates the data that is retrieved from the database.
* Presentation services
This is the user interface.
The presentation services must be able to manipulate the data into an understandable form.
Source:
Microsoft SQL Server 2000 Administrator's Companion eBook