chapter 7 review

Question 1

t or f: entity relation model forms the basis of an entity relation diagram

Answer 1

true

Question 2

… represents conceptual DB as viewed by end users

Answer 2

ERD

Question 3

ERDs depict DBs main components which are:
e
a
r

Answer 3

entity
attribute
relationships

Question 4

refers to entity set and not single entity occurrence

Answer 4

entity

Question 5

what is the shape of a crow’s foot model?

Answer 5

rectangle

Question 6

characteristics of entities?

Answer 6

attributes

Question 7

attributes represented by ovals connected to entity rectangle with a line

Answer 7

Chen notation

Question 8

…. attributes written in an attribute box below the entity rectangle

Answer 8

crows foot notation

Question 9

attributes that must have a value

Answer 9

required attributes

Question 10

maybe left empty

Answer 10

optional attributed

Question 11

set of possible values for an attribute

Answer 11

domain

Question 12

one or more attributes that uniquely identify each entity instance

Answer 12

identifiers

Question 13

primary key composed of more than one attribute

Answer 13

composite identifiers

Question 14

t or f: composite attributes can’t be subdivided

Answer 14

false

Question 15

t or f: simple attributes can be subdivided

Answer 15

false

Question 16

value may be calculated from other attributes

Answer 16

derived attributes

Question 17

t or f : relationship classification is difficult to establish if only one side of the relationship is known

Answer 17

true

Question 18

describe the relationship classification

Answer 18

connectivity

Question 19

expresses a minimum number of entity occurrences associated with one occurrence of a related entity

Answer 19

cardinality

Question 20

an entity exists in DB only when it is associated with another related entity occurrence

Answer 20

existence dependence

Question 21

entity can exist apart from one or more related entities

Answer 21

existence independence

Question 22

exists if PK of related entity doesnt contain PK component of parent entity

Answer 22

weak relationship

Question 23

exists if PK of related entity does contain PK component of a parent entity

Answer 23

strong entity

Question 24

weak entity meets two conditions:
e
p

Answer 24

existence-dependant

primary key partially or totally derived from parent entity in relationship

Question 25

one entity occurrence doesn’t require corresponding entity occurrence in a particular relationship

Answer 25

optional participation

Question 26

one entity occurrence requires corresponding entity occurrence in particular relationship

Answer 26

mandatory participation

Question 27

the association is maintained within a single entity

Answer 27

unary relationship

Question 28

two entities are associated

Answer 28

binary relationship

Question 29

three entities are associated

Answer 29

Trenary relationship

Question 30

….. used to implement m:n relationship

Answer 30

associative entities

Question 31

t or f: DB designers must make design compromises?

Answer 31

true

Question 32

…. design standards, processing speed, information requirements

Answer 32

conflicting goals

Question 33

t or f: it is not important to meet logical requirements and design conventions

Answer 33

false