DB Programming Chapter 6 Adv. Data Modeling (Lecture)

natural key

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

discriminator

A specialization hierarchy provides the means to define a special supertype attribute known as the subtype ______

1:1

A specialization hierarchy reflects the ________ relationship between EMPLOYEE and its subtypes.

foreign keys in

A supertype contains those attributes that are ________ all of its subtypes

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

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

subtype discriminator

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

design

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

fan

A(n) ________ trap 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.

cluster

An entity ________ is a "virtual" entity type used to represent multiple entities and relationships in the ERD.

primary key

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

1:1

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

specialization

Entity supertypes and subtypes are organized in a(n) ________ hierarchy.

at least one

Every subtype can have ________ supertype to which it is directly related.

category

In MS Visio, you select the subtype discriminator when creating a category using the ________ shape from the available shapes

nulls

In a data model, grouping employees into types avoids unnecessary ________ in the employee attributes.

lattices

In addition to the normal behavior, the EER model also supports specialization________ where a subtype can have multiple parents (supertypes).

subtype

In an aviation company's data model, a PILOT entity might be a(n) ________ of the EMPLOYEE entity.

supertype

In modeling terms, the ________ contains the common characteristics and the entity subtypes contain the unique characteristics of each entity subtype.

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

In specialization hierarchies with multiple levels of supertype/subtypes, a lower-level subtype ________.

attributes

It is common to avoid the display of ________ in an ERD that uses entity clusters.

primary key

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

clustering

The EER model builds on ER concepts and adds support for entity supertypes, subtypes, and entity ________.

completeness

The ________ constraint specifies whether each entity supertype occurrence must also be a member of at least one subtype.

primary key

The ________'s function is to guarantee entity integrity.

supertype

The implementation of disjoint subtypes is based on the value of the subtype discriminator attribute in the ________

inheritance

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

IS

The relationships depicted within the specialization hierarchy are sometimes described in terms of "____-A" relationships.

child entity

What is another name for a subtype?

enhanced

What is another name for the extended entity relationship model?

numeric

What is the best data type for a primary key?

equal to

What is the default comparison condition for the subtype discriminator attribute?

1

What is the ideal number of attributes used to make up a primary key?

improve the readability of the ERD

What is the purpose of an entity cluster?

composite key

What type of primary key should be used as an identifier of a composite entity?

optional

When defining a 1:1 relationship where one side of the relationship is mandatory and one is optional, where should the foreign key be placed?

surrogate

_______ primary keys are especially helpful when there is no natural key.

time-variant

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

generalization

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

specialization

________ is the top-down process of identifying lower-level, more specific entity subtypes from a higher-level entity supertype.

redundant

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

disjoint

________ subtypes are subtypes that contain a unique subset of the supertype entity set.

overlapping

________ subtypes are subtypes that contain nonunique subsets of the supertype entity set.