3.1 The ER MODEL

Question 1

is a conceptual model that represents the information structure of a problem domain in terms of entities and relationships.

Answer 1

entity-relationship model (ERM)

Question 2

Who developed ERM

Answer 2

Dr. Peter Pin-Shan Chen

Question 3

When was the ERM developed

Answer 3

1976

Question 4

is a type of structural diagram for use in database design.

Answer 4

Entity Relationship Diagram (ERD)

Question 5

What are the 3 basic elements of ERD

Answer 5

Entity
Attributes
Relationship

Question 6

is a person, place, object, event, or concept about which the organization wishes to maintain data.

Answer 6

entity type

Question 7

represents a collection of all entities that share common properties or characteristics. The entity type is described once in the database using meta

Answer 7

entity type

Question 8

is a single occurrence of an entity type. For example; Mary, John, and Tom are 3 instances of the EMPLOYEE entity type.

Answer 8

entity instance

Question 9

are the properties or characteristics of an entity. Each entity type has a set of attributes associated with it.

Answer 9

Attributes

Question 10

association among one or more entities

Answer 10

relationship

Question 11

is a meaningful association between or among entity types.

Answer 11

Relationship Type

Question 12

is the association between specific entity instances.

Answer 12

Relationship Instance

Question 13

was introduced by Peter Chen, who developed entity-relationship modeling and published his work in 1976. This notation was one of the pioneers in software and information system modeling and design.

Answer 13

Chen Notation

Question 14

is used in Barker’s Notation, SSADM and Information Engineering. Crow’s Foot diagrams represent entities as boxes and relationships as lines between the boxes. Different shapes at the ends of these lines represent the cardinality of the relationship. Many preferred to use Crow’s Foot notation due to its simplicity.

Answer 14

Crow’s Feet Notation

Question 15

Name the 3 types of entities

Answer 15

Entity / Strong Entity, Weak Entity, Associative Entity

Question 16

This is an attribute that uniquely identifies a particular entity. The name of a key attribute is underlined in Chen Notation. In Crow’s Foot Notation, key attributes are also underlined. Aside from underline, it is also indicated with PF or FK depending on, if the key attribute is a primary key or foreign key (to be discussed in the succeeding module).

Answer 16

Key Attribute

Question 17

This is an attribute of the weak entity that when combined with the key attribute of the parent entity, provides a unique identification for the weak entity. Chen notation underlines the discriminator with a dashed line. In Crow’s Foot Notation, the key attribute of the weak entity became composite, constituting the key attributes of the parent’s and the child’s.

Answer 17

Partial Key Attribute (discriminator)

Question 18

An attribute that can have many actual values. For instance, a person may have several college degrees, or a household may have several different phones, each with its own number.

Answer 18

Multivalued Attribute

Question 19

This is an attribute whose value is calculated (derived) from other attributes. The derived attribute may or may not be physically stored in the database. In the Chen notation, this attribute is represented by a dashed oval.

Answer 19

Derived Attribute (or computed attribute)

Question 20

An attribute that can be further subdivided into smaller parts.

Answer 20

Composite Attribute

Question 21

his is a relationship where the entity is strong and independent of other entities, and the Primary Key (PK) of child entry does not contain the PK component of the parent entity.

Answer 21

Strong Relationship

Question 22

A relationship where child entity is existence-dependent on the parent entity, and PK of Child Entity contains PK component of Parent Entity. This relationship is represented by a double rhombus.

Answer 22

Weak Relationship / Identifying Relationship

Question 23

A _______ of a Relationship is the number of relationship instances an entity can participate

Answer 23

Cardinality of Relationship

Question 24

Each entity instance in one side of the relationship will have exactly one related entity instance on the other side of the relationship

Answer 24

One–to–One Relationship

Question 25

A maximum of one entity instance on one side of the relationship can have more than one related entity instances on the other side of the relationship.

Answer 25

One–to–Many Relationship

Question 26

More than one entity instances on one side of the relationship can have a maximum of one entity instance on the other side of the relationship

Answer 26

Many-to-One Relationship

Question 27

Entities on both sides of the relationship can have more than one related entity on the other side of the relationship.

Answer 27

Many–to–Many Relationship

Question 27

Entities on both sides of the relationship can have more than one related entity on the other side of the relationship.

Answer 27

Many–to–Many Relationship

Question 28

one entity occurrence does not require a corresponding entity occurrence in a particular relationship

Answer 28

Optional Participation

Question 29

one entity occurrence requires a corresponding entity occurrence in a particular relationship

Answer 29

Mandatory Participation

Question 30

state the limits of the number of entity occurrences/participations that are associated in a relationship.

Answer 30

Cardinality Constraints

Question 31

If zero, then relationship participation is optional
If one or more, then relationship participation is mandatory

Answer 31

Minimum Cardinality

Question 32

The maximum number of participations of entity instances in a relationship.

Answer 32

Maximum Cardinality

Question 33

is the number of entity types that participated in the relationship.

Answer 33

Degree of Relationship

Question 34

are also known as a recursive relationship. It is a relationship where the same entity participates more than once in different roles.

Answer 34

Unary relationships

Question 35

exists when two entities are associated in a relationship

Answer 35

Binary Relationship

Question 36

Although most relationships are binary, the use of__________ relationships does allow the designer some latitude regarding the semantics of a problem

Answer 36

Ternary Relationship