20.4.1 Object oriented/relational model

In the simple case, a class maps onto a database table, an instance of the class maps onto a record in the table, and a slot in the class maps onto an attribute in the table.

In general, however, a class maps onto a database view, an instance of the class maps onto a collection of records in the view, and a slot in the class is either:

• A base slot that maps onto an attribute in the view
• A join slot that points to a list of other view-class instances

If an instance maps onto more than one record in the view then for each record, all the key attributes from each table in the view are the same.