Which symbol denotes a derived attribute in an ER model?

Concept

In Chen-style entity–relationship notation, attributes are drawn as ellipses, and variations in the outline encode different kinds of attributes. A derived attribute is computed from other stored attribute values instead of being stored independently.

Application

A dashed boundary is the conventional outline used for a computed attribute. Thus, the symbol described as a dashed ellipse denotes a derived attribute.

Contrast

• A double ellipse denotes a multivalued attribute, which can hold more than one value for an entity.

• A squared ellipse is not a standard attribute symbol in Chen notation; entity sets use rectangles, while weak entity sets use double rectangles.

• An underlined attribute name denotes a key attribute, whose value identifies an entity uniquely.

Cross-check

For example, age can be calculated from date of birth and the current date, so age may be drawn as a dashed ellipse. This confirms the dashed-outline convention.

Result: Dashed ellipse.