You are in browse mode. You must login to use MEMORY

level: Level 0

Questions and Answers List

level questions: Level 0

Question	Answer
This is a high level model that represents the requirements and complexities of a complex database.	Enhanced entity-relationship model
This is a generic entity type that has a relationship with one or more subtypes.	Supertype
This is a subgrouping of the entities in an entity type that is meaningful to the organization and that shares common attributes or relationships distinct from other subgroupings.	Subtype
What are the two concepts of EER model?	Generalization Specialization
This is the process of defining a more general entity type from a set of more specialized entity types.	Generalization
This is the process of defining one or more subtypes of the supertype and forming supertype/subtype relationships.	Specialization
These constraints allow you to capture some of the important business rules that apply to these relationships.	Specifying constraints
These are the two most important type of constraints that are described.	Completeness constaints Disjointness constraints
This is a type of constraint that addresses whether an instance of a supertype must also be a member of at least one subtype.	Completeness constraints
These are the two possible rules of the completeness constraints.	Total specialization rule Partial specialization rule
This rule specifies that each entity instance of a supertype must be a member of some subtype in the relationship.	Total specialization rule
This rule specifies that an entity instance of a supertype is allowed not to belong to any subtype.	Partial specialization rule
These constraints addresses whether an instance of a supertype may simultaneously be a member of two (or more) subtypes.	Disjointness constraints
These are the two possible rules of the disjointness constraints.	Disjoint rule Overlap rule
This is the rule that specifies that an instance of a supertype may not simultaneously be a member of two (or more) subtypes.	Disjoint rule
This is the rule that specifies that an instance of a supertype may simultaneously be a member of two (or more) subtypes.	Overlap rule