Topic 5: The Enhanced E-R Model Flashcards
It is used to identify the model that has resulted from extending the original E-R model with new modeling constructs
Enhanced Entity Relationship Model
It is the generic entity type that has a relationship with one or more types
Supertype
It is the subgrouping of the entities in an entity type that is meaningful to the organization
Subtypes
Explain Attribute Inheritance in entitity types
Attribute Inheritance refers to the property wherein subtype entities inherit the values of all attributes and instance of all relationships of the supertype
It refers to the process of defining a more general entity type from a set of more specialized entity types
Generalization
It is the pricess of specifying a more specific entity type from a set of more generalized entity types
Specialization
It specifies that each entity instance of the supertype must be a member of some subtype in the relationship
Total Specialization
It specifes that an entity instance of the supertype is allowed not to belong to any subtype
Partial Specialization
What are Completeness Constraints
It addresses the question of whether an instance of a supertype must also be a member of at least one subtype
What are Disjointness Constraints
It addresses whether an instance of a supertype may simultaneously be a member of two (or more) subtypes
Explain the Disjoint rule of Disjointness Constraints
If an entity instance is a member of one subtype, it cannot simultaneously be a member of other subtypes
Explain the Overlap rule in Disjointness Constraints
Entity instances can be simultaneous
It is an attrubute of a supertype whose values derermine the target subtype or subtypes
Subtype Discriminators
It refers to a hierarchical arrangement of supertypes, where each subtype has only one supertype
Supertype/Subtype hierarchies
It is a set of one or more entity types and associated relationsihips grouped into a single abstract entity type
Entity Clustering
