Modeling Data in the Organization

IS-DBS 313
Presented By:
Dr. Rosemarie S. Guirre
Modeling Data in
the Organization

WRAP UP
The Database Environment and Development Process
Presented By: Dr. Rosemarie S. Guirre | IS-DBS 313-2
Data
Information
Data vs. Information
Database
Metadata
DBMS
Data Dictionary
Data Models
Types of Models
Relational Model
Keys
ERD
Data Mining
Components of DB
DB Dev. Process

Modeling Data in the
Organization
IS-DBS 313-2
1. E-R Model Notation
2. Modeling the Rules of the
Organization
3. Modeling Entities and Attributes
4. Modeling Relationship
TOPICS

Entity-Relationship Model
Models conceptual database design
in terms of entities, attributes, and
relationships between entities
E-R Model
Developed by Chen in 1976
Enhanced E-R model (EER
model)

Entity-Relationship Symbols
Attribute
Relationship
Entity

ER SYMBOLS
Entity Symbols
STRONG ENTITY
ASSOCIATIVE
ENTITY

Entity Symbols
ASSOCIATIVE
ENTITY

Entity Symbols
STRONG ENTITY

Entity Symbols

ER SYMBOLS
Attribute
Symbols
ATTRIBUTE
{MULTIVALUED}
ATTRIBUTE
[DERIVED]
ATTRIBUTE

Attribute
Symbols
STRONG ENTITY

Attribute
Symbols
ATTRIBUTE

Attribute
Symbols
{MULTIVALUED}
ATTRIBUTE

Attribute
Symbols
[DERIVED]
ATTRIBUTE

ER SYMBOLS
Relationship
Symbols
RELATIONSHIP
IDENTIFYING
RELATIONSHIP

Types of
Relationship
Symbols

Identify ER
Symbols
Attribute
Relationship
Entity

ER SYMBOLS
MANDATORY ONE
MANDATORY MANY
OPTIONAL ONE
OPTIONAL MANY
MANY TO MANY

MANDATORY
ONE

OPTIONAL
MANY

MANY
TO
MANY

MANDATORY
MANY

OPTIONAL
ONE

ER SYMBOLS
UNARY
One entity
BINARY
2
1 TERNARY
2
1
3
2 entities
3 entities

E-R Model Constructs
person, place, object, event, concept
(often corresponds to a row in a table)
Entity (instance)
collection of entities (often
corresponds to a table)
Entity Set or Type
Entities

Strong vs Weak
Entities
exist independently of other types
of entities
has its own unique identifier
represented with single-line
rectangle
STRONG ENTITY

Strong vs Weak
Entities
Does not have a unique identifier
dependent on a strong
entity…cannot exist on its own
represented with double-line
rectangle

STRONG
ENTITY
WEAK
ENTITY
EMPLOYEE HAS
emp_id emp_name date_of_birth
dep_name
mid_name
first_name
last_name

Analyze
the flow

Entity has attributes links together
All relationships for the associative entity
should be many
Independent of the other entities
ASSOCIATIVE
ENTITY
preferably has a unique identifier, and
should also have other attributes
participating in other relationships other than
the entities of the associated relationship

ASSOCIATIVE
ENTITY
CERTIFICATE
ASSOCIATIVE ENTITY
EMPLOYEE COURSE
emp_id emp_name
cert_num date_completed
course_id course_title

What Should an
Entity Be?
An object that will have many
instances in the database
SHOULD BE:
An object that will be composed of
multiple attributes
An object that are trying to model

An Entity Should
Not Be?
A user of the database system
An output of the database
system (e.g. a report)

RECAPITULATION
ENTITY
SYMBOL
S
ATTRIBUTE
SYMBOL
S
RELATIONSHIP
SYMBOL
S
RELATIONSHIP
CARDINALIT
IES
RELATIONSHIP
DEGREE
S

INAPPROPRIATE
ENTITIES
System user System output
Appropriate entities

Entities
THINGS
TANGIBLE
ROLES
PLAYED
ORGANIZA-
TIONAL UNITS DEVICES
INCIDENTS,
EVENTS,
INTERACTIONS
SITES
LOCATIONS
Airplane
Book
Vehicle
Document
Worksheet
Employees
Customer
Doctor
Patient
End User
System
Admin
Division
Department
Section
Task Force
Work group
Sensor
Timer
Controller
Printer
Keyboard
Mouse
Button
Flight
Service Call
Logon
Logoff
Contract
Purchase
Payment

property or characteristic of
an entity or relationship type
(often corresponds to a
column in a table)
Attributes

Primary Key - unique
Types of Attributes
Foreign Key – PK in another
DB

Simple versus Composite Attribute
Classification of
Attributes
Single-Valued versus Multivalued Attribute
Stored versus Derived Attributes
Identifier Attributes

Composite Attributes
address
street_add
city state
postal_code

ATTRIBUTE
{MULTIVALUED}
ATTRIBUTE
[DERIVED]
ATTRIBUTE

Multivalued and
Derived Attributes
emp_name
emp_id add
date_employed
year_employed skill
employee

Relationship Set or Type
link between entities (corresponds to
primary key-foreign key equivalencies
in related tables)
Relationship (instance)
category of relationship…link
between entity types
Relationship

between
specific
entity
instances
(instance)
lines
between
entity type
Relationship
(set or type)
vs

ER SYMBOLS
MANDATORY ONE
MANDATORY MANY
OPTIONAL ONE
OPTIONAL MANY
MANY TO MANY ONE TO ONE
ADDITIONAL

Prepared By: Dr. Rosemarie S. Guirre | IS-DBS 313-2
END OF MODULE 1

Modeling Data in the Organization

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