INSY 3304 CH 5

The specialization hierarchy provides a means to ________.

define a subtype discriminator

A(n) ________ occurs when a relationship is improperly or incompletely identified and, therefore, is represented in a way that is not consistent with the real world.

design trap

Subtypes that contain a unique subset of the supertype entity set are known as ________.

disjoint subtypes

The extended entity relationship model is also known as ________.

enhanced entity relationship model

In modeling terms, the ________ contains common characteristics.

entity supertype

A(n) ________ occurs when you have one entity in two 1:M relationships to other entities, thus producing an association among the other entities that is not expressed in the model.

fan trap

Every subtype can ________.

have only one supertype to which it is related

The property of ________ enables an entity subtype to gain the attributes and relationships of the supertype.

inheritance

A ________ refers to a real-world, generally accepted identifier used to distinguish real-world objects.

natural key

Subtypes that contain nonunique subsets of the supertype entity set are known as ________.

overlapping subtypes

Arguably, the most important characteristic of an entity is its ________.

primary key

One important inheritance characteristic is that all entity subtypes inherit their ________ from their supertype.

primary key attribute

The purpose of an entity cluster is to ________.

simplify the entity relationship diagram (ERD)

A(n) ________ is the attribute in the supertype entity that determines to which subtype each supertype occurrence is related.

subtype discriminator

A ________ is especially helpful when there is no natural key.

surrogate primary key

When defining a 1:1 relationship where one side of the relationship is mandatory and one is optional, ________.

the foreign key should be placed in the table that defines the optional entity

When defining a 1:1 relationship where both sides of the relationship are mandatory, ________.

the foreign key that causes the fewest nulls should be selected

A specialization hierarchy reflects the ________.

1:1 relationship between an entity supertype and its subtypes

Which of the following is an example of time-variant data?

A person's bank account balance

Which of the following is the most preferred data type for a primary key?

Numeric

________ are used to implement relationships among entities.

Primary keys and foreign keys

________ occur when there are multiple relationship paths between related entities.

Redundant relationships

In specialization hierarchies with multiple levels of supertype/subtypes, ________.

a lower-level subtype inherits all of the attributes and relationships from all of its upper-level supertypes

A weak entity in a strong identifying relationship with a parent entity is normally used to represent ________.

a real-world object that is represented in the data model as two separate entities in a strong identifying relationship

In MS Visio, the completeness constraint is based on the ________.

category shape

An entity subtype ________.

contains its own unique characteristics

The ________ adds support for entity supertypes, subtypes, and entity clustering.

extended entity relationship model

One of the characteristics of a primary key is that ________.

it uniquely identifies each entity instance

A primary key's function is to ________.

uniquely identify an entity instance or row within a table

At the implementation level, the supertype and its subtype(s) depicted in the specialization hierarchy maintain a ________.

1 : 1 relationship

Which of the following is true of entity supertypes and subtypes?

A supertype contains those attributes that are common to all of its subtypes.

Which of the following types of primary key is useful to represent M:N relationships?

Composite key

________ is the bottom-up process of identifying a higher-level, more generic entity supertype from lower-level entity subtypes.

Generalization

________ refer to data whose values change in the future and for which you must keep a history of the data changes.

Time-variant data

In a specialization hierarchy constraint scenario with partial overlapping constraint, ________.

an entity supertype has optional subtypes

In an organization's data model, employees are grouped to ________.

avoid nulls when some employees have characteristics that are not shared by other employees