Modern Database Management - Chapter 3

Answer: FALSE

52) Supertype/subtype relationships should be used when the instances of a subtype participate in no relationships which are unique to that subtype.

Answer: TRUE

68) A subtype can become a supertype if the subtype has other subtypes beneath it.

Answer: TRUE

70) In a supertype/subtype hierarchy, attributes are assigned at the highest logical level that is possible in the hierarchy.

Answer: FALSE

71) Subtypes at the lowest level of a hierarchy do not inherit attributes from their ancestors.

Answer: TRUE

72) Entity clustering is a methodology for grouping one or more entity types and associated relationships into a single abstract entity type.

Answer: TRUE

83) It is easier t o share information across organizations if companies in the same industry use the same universal data model as the basis for their organizational databases.

Answer: FALSE

84) Adapting a packaged data model from your DBMS vendor makes it difficult for the application to work with other applications from the same vendor.

Answer: TRUE

85) Because a purchased data model is extensive, you begin by identifying the parts of the data model that apply to your data modeling situation.

Answer: FALSE

86) You will never need to map data in current databases to data in a packaged data model.

only one supertype.

In a supertype/subtype hierarchy, each subtype has:

Answer: FALSE

59) 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.

Answer: TRUE

60) 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.

Answer: FALSE

66) When subtypes are overlapping, an additional field must be added to the supertype to act as a discriminator.

Answer: FALSE

78) Packaged data models cause projects to take more time to build.

Answer: TRUE

79) Packaged data models can be developed using proven components.

Answer: FALSE

80) Data models of an existing database are harder for data modelers to read.

FALSE

A subtype is a generic entity that has a relationship with one or more entities at a lower level.

require customization.

Packaged data models:

Answer: TRUE

73) An entity cluster should focus on some area of interest to some community of users, developers or managers.

Answer: TRUE

74) 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.

Answer: TRUE

75) Packaged data models are meant to be customized.

Answer: FALSE

76) Packaged data models use an entity type to store union data.

determining the business rules that will be established through the data model.

The most important challenge of customizing a purchased data model is:

map data to be used from package to data in current databases.

The third step in the data modeling process with a packaged data model is:

essential components and structures are already defined.

Using a packaged data model, projects take less time and cost because:

entities.

When identifying with the parts of the packaged data model that apply to your organization, you should first start with:

universal data model.

A generic or template data model that can be reused as a starting point for a data modeling project is called a(n):

data profiling.

A good method for identifying inconsistencies and finding hidden meaning in the customized purchased data model is:

FALSE

A member of a subtype does NOT necessarily have to be a member of the supertype.

more one-to-one relationships give the data model more flexibility.

All of the following are advantages of packaged data models EXCEPT:

utilize all business rules that come with the packaged data model.

All of the following are steps to using a packaged data model EXCEPT:

none of the above.

An attribute of the supertype that determines the target subtype(s) is called the:

all of the above.

An entity cluster can be formed by:

a set of one or more entity types and associated relationships grouped into a single abstract entity type.

An entity cluster is:

TRUE

An entity instance of a subtype represents the same entity instance of the supertype.

TRUE

One of the major challenges in data modeling is to recognize and clearly represent entities that are almost the same.

disjoint

The ________ rule specifies that an entity can be a member of only one subtype at a time.

partial specialization

The ________ rule specifies that an entity instance of a supertype is allowed not to belong to any subtype.

total specialization

The ________ rule specifies that each entity instance of the supertype must be a member of some subtype in the relationship.

overlap

The ________ rule states that an entity instance can simultaneously be a member of two (or more) subtypes.

Total specialization

Which of the following is a completeness constraint?

Answer: TRUE

53) Specialization is the reverse of generalization.

Answer: FALSE

54) Generalization is a top-down process.

Answer: TRUE

55) A completeness constraint may specify that each entity of the supertype must be a member of some subtype in the relationship.

Answer: FALSE

56) The total specialization rule states that an entity instance of a supertype is allowed not to belong to any subtype.

Answer: FALSE

58) When the total specialization rule is set for a supertype/subtype relationship, one could roughly compare the supertype to an abstract class in object-oriented programming.

Answer: TRUE

77) A universal data model is a generic or template data model that can be reused as a starting point for a data modeling project.

Answer: TRUE

81) Packaged data models are as flexible as possible because all supertype/subtype relationships allow the total specialization and overlap rules.

Answer: FALSE

82) Creating a data model from a packaged data model requires much more skill than creating one from scratch.

Answer: TRUE

87) Mapping existing data to new data in a packaged data model is useful for developing migration plans.

Answer: TRUE

88) It is easy to miss the opportunity to visualize future requirements shown in the full data model when using a packaged data model.

disjointedness constraint

A ________ addresses whether an instance of a supertype may simultaneously be a member of two or more subtypes.

completeness

A ________ constraint is a type of constraint that addresses whether an instance of a supertype must also be an instance of at least one subtype.

supertypes

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.

total specialization and overlap

In packaged data models, all subtype/supertype relationships follow the ________ and ________ rules.

M:N relationships

In packaged data models, strong entities always have ________ between them.

there are attributes that apply to some but not all instances of an entity type.

Subtypes should be used when:

generalization.

The process of defining a more general entity type from a set of more specialized entity types is called:

specialization.

The process of defining one or more subtypes of a supertype and forming relationships is called:

attribute inheritance.

The property by which subtype entities possess the values of all attributes of a supertype is called:

overlap rule.

The subtype discriminator is a composite attribute when there is a(n):

Supertype

Which of the following is a generic entity type that has a relationship with one or more subtypes?