EER modeling

Question 1

taking a ________ to modeling data and relationships in a business process is important because of

Answer 1

standardized approach, the complexity involved

Question 2

enhanced ER diagram

Answer 2

ER diagram that shows subtypes and supertypes of entities and identifies relationships between them

Question 3

supertype

Answer 3

entity type that includes distinct subtypes that needs to be represented in data model

Question 4

subtype

Answer 4

subgrouping of entities in an entity type that is meaningful to org and shares common attributes/relationships distinct from other subgroups

Question 5

how to show subtype and supertype on EER diagram

Answer 5

• subtypes are like branches under supertype (connected by circle under subtype)
• supertype contains all attributes shared by all subtypes
• subtypes only contain additional attributes that are unique to them

Question 6

example of sub and supertypes

Answer 6

supertype: employee, all entity instances have employee ID, name, address, and date hired

subtypes: hourly (hourly rate attribute), salaried (annual salary and stock option attributes), consultant (contract number and billing rate attributes)

Question 7

first steps to EER diagram

Answer 7

• identify a set of entities that share a set of common attributes
• attempt to identify supertype with maximum number of common attributes

Question 8

relationships at the supertype level indicate that

Answer 8

all subtypes will participate in the relationship

Question 9

if a relationship is shown at the subtype level

Answer 9

only instances part of that subtype participate in relationship

Question 10

2 processes for identifying supertypes and subtypes

Answer 10

generalization and specialization

Question 11

generalization

Answer 11

process of minimizing the differences between entities by identifying their common features and aggregating them into a supertype, with subtypes for leftover attributes

Question 12

generalization is a

Answer 12

bottom-up approach (creates smaller number of entity types from a larger number)

Question 13

potential downside of generalization

Answer 13

being too general and having too few entity types, leaving out important details

Question 14

specialization

Answer 14

identify relevant differences between entities and splitting them into necessary subtypes

Question 15

specialization is a

Answer 15

bottom-down approach

Question 16

potential byproduct of generalization

Answer 16

realizing an entity had no particular distinguishing characteristics and has no need to be a subtype

Question 17

subtype discriminator

Answer 17

attribute of supertype whose values determine target subtype

Question 18

example of subtype discriminator

Answer 18

attribute Employee_type can be H, S, or C, each representing 3 subtypes of employee supertype

Question 19

why use subtype discriminator

Answer 19

speed up data retrieval if there are large number of subtypes

Question 20

constraints are

Answer 20

intuitive, help us manifest business rules and incorporate them into EER design

Question 21

participation constraint

Answer 21

dictate whether every member of superclass must participate as a member of a subclass

Question 22

disjoint constraints

Answer 22

define whether it is possible for an instance of a superclass to be a member of one or more subclasses simultaneously

Question 23

disjoint rule

Answer 23

disjoint constraint specifies that if subtypes of specialization are disjoint then an entity can be a member of only one subtype

Question 24

non-disjoint (overlap) rule

Answer 24

if subtypes of specialization are not disjoint then an entity may be a member of more than one subtype

Question 25

represent disjoint rule

Answer 25

circle with d inside connected to rectangle, multiple subtypes connected to circle with curve on line

Question 26

represent overlap rule

Answer 26

circle with o inside connected to rectangle, multiple subtypes connected to circle with curve on line

Question 27

participation constraints addresses the question

Answer 27

does an instance of a supertype have to be a member of at least one of the subtypes or not?

Question 28

total specialization

Answer 28

every instance of supertype has to belong to a subtype

Question 29

partial specialization

Answer 29

every entity in supertype does not need to be in any subtype

Question 30

representation of total specialization

Answer 30

double line from entity to circle with letter inside

Question 31

total and disjoint constraint combination

Answer 31

- double line, d in circle - supertype entity must also be exactly one of the subtypes

Question 32

total and overlapping constraint combination

Answer 32

- double line, o in circle - supertype entity must be at least one of the subtypes

Question 33

partial and disjoint constraint combination

Answer 33

- single line, d in circle - if supertype entity is part of subtype, it must be a part of exactly one of them

Question 34

partial and overlapping constraint combination

Answer 34

- single line, o in circle - supertype entity can be a part of some, all, or none of the subtypes