Modern Database Management - Self Check 03
Supertype/Subtype relationships should be used when the instances of a subtype participate in no relationships which are unique to that subtype.
F
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.
F
Generalization is a top-down process.
F
A completeness constraint may specify that each entity of the supertype must be a member of some subtype in the relationship.
T
A subtype can become a supertype if the subtype has other subtypes beneath it.
T
Packaged data models are meant to be customized.
T
A ________ is a constraint that addresses the question of whether an instance of a supertype may simultaneously be a member of two or more subtypes.
disjointness constraint
A(n) ________ is a set of one or more entity types and associated relationships grouped into a single abstract entity type.
entity cluster
The ________ specifies that each entity instance of the supertype must be a member of some subtype in the relationship.
total specialization rule
A packaged data model can either be ________ or ________.
universal; industry specific
Attribute inheritance is a property of subtype entities where they inherit ________ of all attributes of the supertype.
values
A member of a subtype does NOT necessarily have to be a member of the supertype
F
A subtype is a generic entity that has a relationship with one or more entities at a lower level.
F
Creating a data model from a packaged data model requires much more skill than creating one from scratch.
F
Data models of an existing database are harder for data modelers to read
F
Packaged data models cause projects to take more time to build.
F
Packaged data models use an entity type to store union data.
F
Subtypes at the lowest level of a hierarchy do not inherit attributes from their ancestors
F
When subtypes are overlapping, an additional field must be added to the supertype to act as a discriminator.
F
A universal data model is a generic or template data model that can be reused as a starting point for a data modeling project.
T
An entity cluster can have a relationship with another entity cluster much the same way that an entity can have a relationship with another entity.
T
An entity cluster should focus on some area of interest to some community of users, developers or managers.
T
An entity instance of a subtype represents the same entity instance of the supertype.
T
Entity clustering is a methodology for grouping one or more entity types and associated relationships into a single abstract entity type.
T
In a supertype/subtype hierarchy, attributes are assigned at the highest logical level that is possible in the hierarchy.
T
Packaged data models are as flexible as possible because all supertype/subtype relationships allow the total specialization and overlap rules
T
Packaged data models can be developed using proven components.
T
Specialization is the reverse of generalization.
T
The overlap rule specifies that if an entity instance of the supertype is a member of one subtype, it can simultaneously be a member of two (or more) subtypes
T
You should consider using supertype/subtypes when there are ________ that apply to some (but not all) instances of an entity type.
attributes
A ________ constraint is a type of constraint that addresses whether an instance of a supertype must also be a member of at least one subtype.
completeness
The ________ specifies that an entity instance can simultaneously be a member of two or more subtypes.
overlap rule
The process of defining one or more subtypes of the supertype and forming supertype/subtype relationships is called ________.
specialization
A subgrouping of the entities in an entity type that shares common attributes or relationships is called a(n) ________.
subtype
An attribute of the supertype whose values determine the target subtype(s) is called a(n) ________.
subtype discriminator
A supertype/subtype hierarchy is an arrangement of supertypes and subtypes where each ________ has only one ________.
subtype, supertype
