An entity subtype is a collection of entities of the same entity type to which a narrower definition and additional predicates apply. That is to say, entity types can be sub-typed, if there are entities of that type which have unique definitions, attributes, or relationships.
In the following example, the entity type Care Provider can be sub-typed into Doctors and Nurses. There should be unique attributes and relationships that entities of the Doctor sub-type has that entities of the Nurse subtype does not and vice-versa. Additionally, there should be a valid business reason for sub-typing. A valid business reason would exist if there were additional business processes involved with one sub-type and not the other.
The eGolf Services data model does not need subtypes.
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