The Functions of a Domain

Each domain specification provides one or more of the following:

Storage definitions

From which APPX determines the internal storage length and format of any field that references the domain.

Display characteristics

For items painted on an image, such as display masks or justification options.

Constraints and restrictions

On a field’s valid values, including range checks, validation tables, edit masks, and data lookup.

Other field attributes

Including column headings, descriptive names, default values, and security codes.