Starting from weak and strong entities

Question 1

Strong entities are denoted by:

Answer 1

Rectangles

Question 2

Weak entities are denoted by:

Answer 2

Double rectangles

Question 3

What are attributes?

Answer 3

descriptive properties of entities and denoted by ovals

Question 4

What are keys

Answer 4

kinda like attributes but uniquely identified

Superkey: umbrella term for a set of one or more attributes taken to identify an entity occurrence

Candidate: minimal set(one)

composite: superkey but starts with 2

Primary key: chosen principal means of identifying

Question 5

Vrai ou faux: A key (primary, candidate, and super) is a property of the individual entity occurrences , rather than of the entity set.

Answer 5

Faux, reverse it

Question 6

How do you denote primary keys:

Answer 6

underline the names…all for composite

Question 7

Relationship?

Answer 7

Single…meaningful association among entities, represented by a diamond and weak by double diamond

Question 8

Relationships within an entity is possible…

Answer 8

OUI

Question 10

Multiplicity

Answer 10

Constraint on relationships, cardinality and participation

Question 10

Cardinality

Answer 10

Maximum number of occurrences

Question 11

Participation

Answer 11

Determines whether all or only some entity occurrences participate in a relationship.
Total is bold line ou double

Question 13

Problems with ER models

Answer 13

Some constraints can’t be captured

Subjective

Hard to decide if it is an attribute, relation or entity

Cause connection traps

Question 14

What are connection traps and examples:

Answer 14

problem caused by designing a conceptual data model.

Fan trap : pathway between certain entity occurrences is ambiguous

Chasm trap:
model suggests the existence of a relationship between entity types, but pathway does not exist between certain entity occurrences that creates information gap

Question 15

Specialization?

Answer 15

EER concept, designating subgroups within an entity set.

Question 16

Super and sub class

Answer 16

entity type with >= 1 subgroupings

Subgrouping

Both written in rectangle with ISA in it

Question 17

Generalization

Answer 17

EER, opposite of specialization