The image datatype.gif shows a Consumer table with an Interest column storing the expressions that capture a consumer’s interest in cars. The image also shows an attribute set, Car4Sale, that defines the list of elementary attributes used in the expressions and includes a list of approved functions.

The Consumer table contains information such as the consumer’s ID, postal code, and phone number. It also shows the consumer’s interests in a car. For example, Model = Taurus, Price < 15000, and Mileage < 25000.