Enhanced Entity-Relationship (EER) Model

Question 1

Additional semantic data modeling concepts incorporated into ER model to
reflect the data properties and constraints more precisely

Answer 1

Enhanced Entity-Relationship (EER) Model
also called Extended ER Model

Question 2

A subset of an entity set with a meaningful (or an explicit need for) subgrouping

Answer 2

Subclass (or Subtype)

Question 3

Entity set from which the subgroupings were formed

Answer 3

Superclass (or Supertype)

Question 4

Also called superclass/subclass or supertype/subtype relationship

Also called an IS-A (or IS-AN) relationship

Answer 4

Class/Subclass Relationship

Question 5

Subclasses inherit all the
attributes and relationship types of their superclass(es)

Answer 5

Inheritance (or Type Inheritance)

Question 6

Process of defining a set of
subclasses of an entity type

Maximizes the difference between the set of subclasses

Used in top-down conceptual
refinement process

Answer 6

Specialization

Question 7

Process of defining a generalized entity type from given entity types

Suppresses (minimizes) the
differences between entity types by identifying their common features

Used in bottom-up conceptual
synthesis process

Answer 7

Generalization

Question 8

Specialization vs Generalization

Answer 8

Specialization starts with a superclass, and defining a set of subclasses from it. Generalization on the other hand starts with specialized entity types and defining a generalized entity type (Superclass) from it.

Question 9

Why include Class/Subclass Relationships?

Answer 9

1. Certain attributes may apply to some but not all entities of the superclass entity type
2. Some relationship types may be participated in only by entities that are members of the
   subclass

Question 10

Subclass membership can be determined by placing a condition on the value
of some attribute of the superclass

Defining predicate is written next to the line connecting subclass to circle

Answer 10

Predicate-Defined Subclasses
(Condition-defined subclasses)

Question 11

Subclass membership condition determined by the same attribute of the superclass

Answer 11

Attribute-Defined Subclasses

Question 12

Subclass membership is determined by the (would-be) database users

Answer 12

User-Defined Subclasses

Question 13

Constraints (on Specialization/Generalization)

Answer 13

Disjointness
Completeness (Totalness)

Question 14

Uses the circle notation to indicate type: disjoint (d) or overlapping (o)

Answer 14

Disjointness

Question 15

Entity can be a member of at
most one of the subclasses of the specialization

Answer 15

Disjoint

Question 16

Entity can be a member of multiple subclasses of the specialization

Answer 16

Overlapping

Question 17

Similar to the Participation constraint on relationship types but on the specialization context

Answer 17

Completeness

Question 18

Specifies that every entity in the
superclass must be a member of at least one subclass in the
specialization

Answer 18

Total Specialization

Question 19

Allows an entity not to belong to any of the subclasses

Answer 19

Partial Specialization

Question 20

TRUE OR FALSE:

Deleting an attribute from a superclass implies that it is automatically deleted
from all subclasses to which it belongs

Answer 20

TRUE

Question 21

Every subclass participates in only one class/subclass relationship (Only single inheritance would exist)

Answer 21

Specialization Hierarchy

Question 22

A subclass can be a subclass in more than one class/subclass relationship (Multiple inheritance would occur)

Answer 22

Specialization Lattice

Question 23

Subclass that represents a collection of entities from different entity types

Has 2 or more superclasses that may represent collections of entities from
distinct entity types

Answer 23

Union Type (or Category)

Question 24

Union Type vs Shared Subclass

Answer 24

Shared subclass is the subset of the intersection of the entity sets, whereas a union type is the union of the entity sets

Question 25

Holds the union of all entities in its superclasses

Answer 25

Total

Question 26

Generalized Superclass vs Union Type

Answer 26

All subclass of a generalized superclass is an instance of it. Contrary, not all instance of entities forming a union type is part of it. (ie. Some cars & some trucks are registered vehicle but not necessarily all, where as all cars and trucks are vehicle)

Question 27

Abstraction concept for building composite objects from their component objects, Combining objects that are related by a particular relationship instance into a higher-level aggregate object (which may be related to another object)

Answer 27

Aggregation

Question 28

TRUE or FALSE Union types should generally be avoided unless the situation definitely warrants this type of construct

Answer 28

TRUE

Question 29

TRUE or FALSE The choice of disjoint/overlapping and total/partial constraints on specialization/generalization is driven by the rules in the miniworld being modeled. If not specified, default would be disjoint and total.

Answer 29

FALSE. default is overlapping and partial