Chapter Two
( Data Model)
Objectives
Introduction to Data Models
 What are the Data Models
 Why they are important
 Learn how to design a DBMS

Data Model:


Model:
Importance of data model:

Relatively simple representations, usually
graphical, of complex real-world data
structures
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Data Model:
Facilitate interaction among the
designer(s), the applications
programmer(s), and the end user(s)
3
Database Models:




Hierarchical Model
Network Model
Relational Model
Entity Relationship (ER) Model
Entity-Relationship Model
(ER-Model)
Purpose of ER Model is to allow the
description of an enterprise to be
written without the attention to the
efficiency or the physical design.
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Entity-Relationship Model (ER-Model)

A set of basic objects called Entity,
and a set of Relationships among
objects (Entities)
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Entity and Entity Set:
Entity:




An object that exists and is distinguishable
from other objects
Car ?
VW?
Entity Set:


A set of entities of the same type
Entity set needs not be disjoint
(Faculty vs Student)
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Entity and Entity Set:

(Continued)
An entity is represented by a set of
attributes
Student(Name, Id, Gpa)

Each attribute has a set of permitted
values called Domain (value set)
Id: positive integer
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Relationship and Relationship Sets:

Relationship is an association
among two or more entities
Faculty and Course

Relationship Set: is a set of
similar relationships
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Business Rules:



Brief, precise, and unambiguous
descriptions of a policies, procedures, or
principles within a specific organization
Apply to any organization that stores
and uses data to generate information
Description of operations that help to
create and enforce actions within that
organization’s environment
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Sources of Business Rules:




Company managers
Policy makers
Department managers
Written documentation




Procedures
Standards
Operations manuals
Direct interviews with the end users
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Translating Business Rules into
Data Model:






Standardize company’s view of data
Constitute a communications tool between
users and designers
Allow designer to understand the nature,
role, and scope of data
Allow designer to understand business
processes
Allow designer to develop appropriate
relationship participation rules and constraints
Promote creation of an accurate data model
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Steps in designing a database using
ER Model
1.
2.
3.
4.
Identify
a.
Entity sets
b.
Relationship sets
Identify semantic Info. In the
relationship sets
Define the value sets of attributes
Organize data into Entity/Relationships
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Database Lifecycle
Analysis:
1.



Study and analyze business
requirements
Interview managers and users for
the information requirements
Develop a system specification
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Database Lifecycle
2.
Design (Data Models)

Entity relational model (ER)
Unify modeling language (UML)

Check the design

3.
Build the Databases/Document/Test


Create tables and views, and programs
Produce manuals
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Database Life Cycle
4.
Product delivery


Load the software
Monitor the performance
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Practice (Analysis):
Discuss a database system for an
organization:
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