An attribute whose value is unique for all instances of the class, but whose content is unimportant.
A nonnegative number used to indicate a count of items, e.g., the number of items in an order.
An amount of money. All bookstore orders are handled in U.S. Dollars.
Note: In a multicurrency system, this type would also identify the currency (U.S. Dollar, Euro, British Pound, etc.) and quite possibly conversion rate information.
A calendar date and time.
The time that elapses between two points in time, expressed in terms of days, hours, minutes, and seconds.
A date specified only to the precision of a month and year.
A calendar year, used primarily for specifying copyright ...