Reference no: EM132225204

There are three very high-level classifications of constraints on data models in database conceptual design: inherent, explicit, and semantic.

Inherent means that the constrain can be fulfilled in the data model implicity.

Explicit means the constraint is fulfilled through a specific "Schema" of the model.

Semantic means the constraint would be fulfilled through application logic and cannot be satisfied within the model itself or any schema of the model.

These make sense in definition but I would appreciate some examples of each and an explanation of why the constrain can be made at the level where it is applied and not at the others.

Reference: https://cs.uwaterloo.ca/~tozsu/courses/CS338/lectures/3%20Constraints.pdf

This link provides a few examples but does not really explain the "Why" for each.

From the link

Constraints - Restrictions on the permitted values in a database state

• Derived from the rules in the miniworld that the database represents

1. Inherent model-based constraints or implicit constraints • Inherent in the data model • e.g., duplicate tuples are not allowed in a relation
2. Schema-based constraints or explicit constraints • Can be directly expressed in schemas of the data model • e.g., films have only one director
3. Application-based or semantic constraints • Also called business rules • Not directly expressed in schemas • Expressed and enforced by application program • e.g., this year's salary increase can be no more than last year's