chapter 2

Question 1

what is a conceptual model

Answer 1

• -> captures the functional and informational needs of the business
• -> it is based on current needs but may reflect future needs
• -> addresses the needs of the business but does not address its implementation
• -> result of completing the data modelling process

Question 2

what does a conceptual model identify

Answer 2

• -> important entities

- -> relationship among entities

Question 3

what does a conceptual model not specify

Answer 3

• -> attributes

- -> unique identifiers

Question 4

why is a conceptual model important for a business

Answer 4

• -> describes exactly the information needs for the business
• -> facilitates discussion
• -> prevents mistakes and understandings
• -> forms important ideal system documentation
• -> forms a sound basis for physical database design
• -> documents the process of the business
• -> takes into account the regulations and laws governing this industry

Question 5

what is a logical model

Answer 5

• -> includes all entities and relationships among them
• -> is called an entity relationship model (ERM)
• -> is illustrated in an ERD
• -> specifies all attributes and UIDs for each entity
• -> determines attribute optionality
• -> determines relationship optionality and cardinality

Question 6

what is a physical model

Answer 6

• -> extension of a logical data model
  - -> defines table definition, data types, and precision
  - -> identifies views, indexes and other database objects
• -> describes how the objects should be implemented in specific database
• -> shows all table structures including columns, primary key, and foreign keys

Question 7

what is data modelling

Answer 7

–> process of capturing the important concepts and rules that shape a business and depicting them visually on a diagram.

Question 8

data models show users the ___________ that their physical models will contain

Answer 8

data

Question 9

a conceptual model is not concerned with how the _________ will be implemented

Answer 9

physical model

Question 10

our technology rich world produces vast quantities of facts in need of ___________

Answer 10

structure and order

Question 11

why is it important to learn about entities

Answer 11

They are things about which we store dat a

Question 12

why is it important to learn about attributes

Answer 12

• -> provide more specific information about the entity

- -> attributes help you distinguish between one instance and another by providing greater detail for the entity

Question 13

what is the example of attributes

Answer 13

–> when you are placing a restaurant order then you have to list the individual food items ordered to calculate the total bill.

Question 14

what is the purpose of unique identifiers

Answer 14

distinguish one instance of an entity from anothe r

Question 15

what is an example of unique identifier

Answer 15

–> in a classroom, you need to distinguish between one student and another

Question 16

what is an entity

Answer 16

• -> something of significance to the business about which data must be known
• -> a name for a set of similar things that you can list
• -> usually a noun
• -> entities have an instance

Question 17

what is an instance

Answer 17

–> an instance is a single occurrence of an entity

Question 18

give 3 examples of entities and instances

Answer 18

entities are

• -> person
• -> job
• -> animal

instances are

• -> steve jobs, elon musk, sheldon cooper
• -> engineer, doctor, lawyer
• -> tiger, shark, monkey

Question 19

entities can be _______, ________ and __________

Answer 19

tangible -> person, product
intangible -> skill level
event -> concert

Question 20

what is an attribute

Answer 20

• -> represents something of significance to the business
• -> describes an entity
• -> quantify an entity
• -> qualify an entity
• -> classify an entity
• -> specify an entity

–> AN ATTRIBUTE HAS A SINGLE VALUE

Question 21

an attribute has values called ____________

Answer 21

data types/formats

–> EACH ATTRIBUTE STORES ONE PIECE OF DATA OF ONE SPECIFIC DATA TYPE

Question 22

what are volatile attributes

Answer 22

some attributes have values that constantly change

Question 23

what are non volatile attributes

Answer 23

Attributes which do not change

Question 24

if given a choice which attribute should you select

Answer 24

non volatile attribute

Question 25

what are mandatory attributes

Answer 25

attributes that must contain a value

Question 26

what are optional attributes

Answer 26

attributes that may either contain a value or be left null

Question 27

what is the purpose of ERD

Answer 27

consistent tool

used to represent the data requirements of a business regardless of the type of database used or even in the absence of one

Question 28

what makes a implementation free model

Answer 28

a good conceptual model is a model which stays the same regardless of the type of database the system is eventually built/implemented on `

–> this is what it means when the model is implementation free

Question 29

what is an entity relationship model

Answer 29

–> list of all entities and attributes as well as all relationships between the entities that are of importance

–> provides background information such as entity descriptions, data types, constraints

–> the model does not require a diagram but a diagram is a very useful tool

Question 30

what are the 4 goals of ER modelling

Answer 30

• -> capture all required data
• -> ensure that data only appears once
• -> locate data in a predictable, logical place
• -> model no data that is derivable from other data already modeled

Question 31

what is a uid made of

Answer 31

attributes and relationships