Chapter 3 Flashcards
Which of the following is true of packaged data models?
Relationships are connected to the highest-level entity type in an order that makes sense.
A completeness constraint may specify that each entity of the supertype must be a member of some subtype in the relationship.
True
In the figure below, the patient must be either an outpatient or a resident patient. This is an example of the ________ rule.
disjoint
Data models of an existing database are harder for data modelers to read.
False
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.
The process of defining a more general entity type from a set of more specialized entity types is called:
generalization.
An entity cluster can be formed by:
combining a strong entity and its weak entities.
Subtypes at the lowest level of a hierarchy do not inherit attributes from their ancestors.
False
The third step in the data modeling process with a packaged data model is:
map data to be used from package to data in current databases.
In packaged data models, all subtype/supertype relationships follow the ________ and ________ rules.
total specialization; overlap
Mapping existing data to new data in a packaged data model is useful for developing migration plans.
True
An entity instance of a subtype represents the same entity instance of the supertype.
True
An entity cluster should focus on some area of interest to some community of users, developers, or managers.
True
The ________ rule specifies that each entity instance of the supertype must be a member of some subtype in the relationship.
total specialization
Which of the following is a completeness constraint?
Total specialization
