The E-R data model provides a wide range of choice in designing a database scheme to accurately model some real-world situation.Some of the decisions to be made are

• Using a ternary relationship versus two binary relationships.
• Whether an entity set or a relationship set best t a real-world concept.
• Whether to use an attribute or an entity set.
• Use of a strong or weak entity set.
• Appropriateness of generalization.
• Appropriateness of aggregation.