Chap 3 Quiz
In packaged data models, strong entities always have ________ between them.
M:N relationships
Which of the following is a generic entity type that has a relationship with one or more subtypes?
Supertype
An entity cluster is:
a set of one or more entity types and associated relationships grouped into a single abstract entity type.
The property by which subtype entities possess the values of all attributes of a supertype is called:
attribute inheritance.
The ________ rule states that an entity instance can simultaneously be a member of two (or more) subtypes.
overlap
The subtype discriminator is a composite attribute when there is a(n):
overlap rule
The ________ rule specifies that an entity instance of a supertype is allowed not to belong to any subtype.
partial specialization
Packaged data models:
require customization.
The process of defining one or more subtypes of a supertype and forming relationships is called:
specialization.
An attribute of the supertype that determines the target subtype(s) is called the:
subtype discriminator.
In a supertype/subtype hierarchy, subtypes that are lower in the hierarchy inherit attributes from not only their immediate supertype but from all ________ in the hierarchy.
supertypes
Subtypes should be used when:
there are attributes that apply to some but not all instances of an entity type.
In packaged data models, all subtype/supertype relationships follow the ________ and ________ rules.
total specialization; overlap
A generic or template data model that can be reused as a starting point for a data modeling project is called a(n):
universal data model.