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Database - ER Model and Business Rules - Discussion
Post your comments here:Name *: Email : (optional) » Your comments will be displayed only after manual approval. Is the process of defining one or more subtypes from a given supertype?Generalization: The process of defining a more general entity type from a set of more specialized entity types. BOTTOM-UP.. Specialization: The process of defining one or more subtypes of the supertype and forming supertype/subtype relationships. TOP-DOWN.. What is Supertype relationships and subtype relationships?A supertype is a generic entity type that has a relationship with one or more subtypes. A subtype is a sub-grouping of the entities in an entity type that is meaningful to the organization and that shares common attributes or relationships distinct from other subgroups.
What type of constraints in Supertype that an instance of a supertype may simultaneously be a member of two or more subtypes *?Disjoint rule; overlap rule. With the disjoint rule an instance of a supertype may be a member of only one subtype at a given time. With the overlap rule an instance of a supertype may simultaneously be a member of two or more subtypes. Structural constraint; operational constraint.
What rule specifies that an entity can be a member of only one subtype at a time?The disjoint rule specifies that if an entity instance of the supertype is a member of one subtype, it MUST simultaneously be a member of another subtype.
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Is the process of defining one or more subtypes of the supertype and forming Supertype subtype relationships?
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