Conceptual Data Model

Question 1

6 steps of the database system development lifestyle

Answer 1

1. planning
2. requirements collection and analysis
3. database design
4. implementation
5. testing and validation
6. deployment and maintenance

Question 2

why is the design stage important

Answer 2

• important to ensure data integrity, efficiency and scalability
• emphasise of what data is needed

Question 3

what 3 database designs are covered in the design stage

Answer 3

1. conceptual
2. logical
3. physical

Question 4

describe the conceptual data model

Answer 4

• high level data model that outlines the system’s data requirements
• to ensure we get precise understanding of the nature of the data and how it is used
• as a model for communication that is nontechnical and free from ambiguities

Question 5

what are used to create the conceptual data model

Answer 5

entity-relationship (E-R) diagrams

Question 6

3 ways of drawing an E-R diagram

Answer 6

1. UML
2. Chen’s notation
3. Crow’s foot

Question 7

describe UML ER diagrams

Answer 7

• rectangle represents an entity
• top word = name of an entity
• bottom word = attribute
• line and arrow = relationship
• number = possible association of one instance of entity to the other associated entity

Question 8

describe chen’s notation ERD

Answer 8

• rectangle = entity
• oval = attribute of an entity
• diamond and lines = relationship
• number = possible association of one instance of entity to the other associated entity

Question 9

describe crow’s foot ERD

Answer 9

• rectangle represents an entity
• top word = name of an entity
• bottom word = attribute
• line = relationship
• crow’s foot = possible association of one instance of entity to the other associated entity

Question 10

describe entities

Answer 10

• group of objects with same properties, having an independent existence
• each instance of an entity is uniquely identified using the primary key attribute

Question 11

whats an entity occurence/ object

Answer 11

each uniquely identifiable object of an entity is called an entity occurrence or an object

Question 12

define strong entity

Answer 12

whose existence is not dependent on another

Question 13

define weak entity

Answer 13

depends upon another entity

Question 14

describe attributes

Answer 14

• property of an entity or relationship
• simple or composite
• associated with the domain

Question 15

how to model attributes

Answer 15

• {PK} = primary key
• {PPK} = partial primary key
• attributes associated with a relationship is shown as a rectangle with a dashed line with the relationship

Question 16

describe relationships

Answer 16

• set of meaningful associations between one or more participating entities
• number of participants in a relationship = degree

Question 17

model relationships

Question 18

what is constraint also known as

Answer 18

multiplicity

Question 19

what are the 2 forms of multiplicity

Answer 19

1. cardinality
2. participation

Question 20

define cardinality

Answer 20

maximum number of possible relationships for an entity participating in a given relationship

Question 21

define participation

Answer 21

whether all or only some instances of an entity participated in a relationship