The complete set of all possible values that an attribute can be assigned is called a domain. A domain is a set of validation criteria that can be applied to more than one attribute; it provides a means of standardizing the characteristics of the attributes. For example, the domain Date, which contains all possible valid dates, can be assigned to any of these attributes:
· Employee Hire Date
· Order Entry Date
· Claim Submit Date
· Course Start Date
An attribute must never contain values outside of its assigned domain. The domain values are defined by specifying the actual list of values or a set of rules. Employee Gender Code, for example, may be limited to the domain of female and male ...