· Visibility – in an object-oriented program, a class and/or its attributes may be accessible to other classes or not. This characteristic is called “visibility” and is very specific to object-oriented design. It is meaningless in an entity/relationship model.
In entity/relationship models, the common set of characteristics for a set of attributes is called a domain. It can be as simple as a format, it could be a list of values, or it could be some sort of validation formula.
Mr. Barker defines a domain as follows:
“A set of business validation rules, format constraints, and other properties that apply to a group of attributes: for example:
· a list of values
· a range
· a qualified list or range ...