Let us understand the conventional programming model before we go into actual implementation of the ORM.

Figure 1

We have a presentation layer that deals with User Interfaces and we have a Business Logic layer which deals with the business rules of the application.  In 3-tier applications we have a dedicated layer that deals with the database related activities called as Data Access layer (DAL).  DAL typically deals with connecting to database executing the commands or stored procedures and getting the resultant sets.