An attribute's value is either a literal or an object identifier.

More Questions from Object-Oriented Database

• Database objects are almost always transient.
• The ODMG Object Model requires that a relationship be specified in both directions.
• An ordered collection of elements of the same type are called sets.
• Specifying a key ensures that no two objects belonging to a class have the same value for the key attribute(s).
• You may specify an object identifier with only one unique tag name.

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