Modern Database Management - Chapter 3

Answer: TRUE

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

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.

FALSE

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

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.

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

Subtypes should be used when:

Supertype

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

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

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: 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: 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

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: 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.

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

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.

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.

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

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.

only one supertype.

In a supertype/subtype hierarchy, each subtype has:

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.

require customization.

Packaged data models:

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.

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

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

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):

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: