For instance, we might want our model to allow only one Age object for each Person object, or at most one object in the President object class when modeling a company.
In an ORM, a constraint restricts the membership of one or more object classes or relationship sets.
The Object-Relationship Model allows analysts to express several different types of constraints:
Special relationship sets including generalization, specialization, aggregation, and association impose restrictions directly on relationship sets and indirectly on object classes.
Here is a short quiz so you can test your understanding of constraints.
Go to the OSA Tutorial ORM
Go to Association Participation Constraints
Last updated 3 Nov 1994. by Mingkang Xu (firstname.lastname@example.org), Lei Cao(email@example.com)