Chapter 5 Questions

Entity supertypes and subtypes are organized in a specialization hierarchy.

The relationships depicted within the specialization hierarchy are sometimes described in terms of is-a relationships

Within an specialization hierarchy, a supertype can exist only within the context of a subtype.

The entity supertype contains the common characteristics and the entity subtypes contain the unique characteristics of each entity subtype.

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

One important inheritance characteristic is that all entity subtypes inherit their primary key attribute from their supertype.

At the implementation level, the supertype and its subtype(s) depicted in the specialization hierarchy maintain a 1:1 relationship

Entity subtypes do not inherit the relationships in which the supertype entity participates

In specialization hierarchies with multiple levels of supertype/subtypes, a lower-level supertype inherits all of the attributes and relationships from all of its upper-level subtype.

An entity supertype can have disjoint or overlapping entity subtypes.

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

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

Implementing non-overlapping subtypes requires the use of one discriminator attribute for each subtype

The completeness constraint can be partial or total.

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

Generalization is based on grouping unique characteristics and relationships of the subtypes.

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

To model time-variant data, you must create a new entity in a M:N relationship with the original entity.

A design 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.

Some designs use redundant relationships as a way to simplify the design.

The extended entity relationship model (EERM) is sometimes referred to as the ____.

____ is a generic entity type that is related to one or more entity subtypes.

The ____ depicts the arrangement of higher-level entity supertypes (parent entities) and lower-level entity subtypes (child entities).

The relationships depicted within the ____ are sometimes described in terms of "is-a" relationships.

Every subtype can have ____ supertype(s) to which it is directly related.

A specialization hierarchy can have ____ level(s) of supertype/subtype relationships.

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

One important inheritance characteristic is that all entity subtypes inherit their ____ key attribute from their supertype.

In the specialization hierarchy there is a ____ relationship between a subtype and supertype.

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

The default comparison condition for the subtype discriminator attribute is the ____ comparison.

Non-overlapping subtypes are subtypes that contain a(n) ____ subset of the supertype entity set.

Overlapping subtypes are subtypes that contain ____ subsets of the supertype entity set.

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

An entity cluster is formed by combining multiple interrelated entities into ____.

The most important characteristic of an entity is its ____ key, used to uniquely identify each entity instance

A ____ key is a real-world, generally accepted identifier used to distinguish that is, uniquely identify-real-world objects.

If one exists, a data modeler uses a ____ as the primary key of the entity being modeled.

The primary key's main function is to uniquely identify a(n) ____ within a table

The "____" characteristic of a primary key states that: The PK must uniquely identify each entity instance. A primary key must be able to guarantee unique values. It cannot contain nulls.

The "____" characteristic of a primary key states that: The selected primary key must not be composed of any attribute(s) that might be considered a security risk or violation. For example, using a Social Security number as a PK in an EMPLOYEE table is not a good idea

The "____" characteristic of a primary key states that: The PK should not have embedded semantic meaning. An attribute with embedded semantic meaning is probably better used as a descriptive characteristic of the entity rather than as an identifier.

Composite primary keys are particularly useful as identifiers of composite entities, where each primary key combination is allowed only once in the ____ relationship.

Surrogate primary keys are especially helpful when there is no ____ key.

____ keys work with primary keys to properly implement relationships in the relational model.

The preferred placement for a foreign key when working with a 1:1 relationship is ____.

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

A ____ 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.

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

According to the data modeling checklist, ____ should clearly define participation and cardinality rules.

The ____________________ is the result of adding more semantic constructs to the original entity relationship (ER) model