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Chapter1Database Modeling Past and Present

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Database ModelingPast and Present

The definition of a database

The definition of a database model

The evolution of database model

The hierarchical and network database models

The relational database model

The object and object-relational database models

Database model types

Database design objectives

Database design methods

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Grasping the Concept of a Database

What is the difference between database and database model?

What is the difference between data and meta data?

The general view of a databaseFirstName LastName Salary

Ahmed Shaheen 5000

Field Type Length

FirstName Char 50

LastName Char 50

Salary int 10

Data

Metadata

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Understanding a Database model

A database model is used to

describe an organized and

ordered set of information

The Relation between

database model and the

application

OLTP applications and OLTP

models

Data warehouse application

and data ware house models

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The Evolution of Database Modeling

Database modeling techniques

are:

1. File Systems

2. Hierarchical Database Model

3. Network Database Model

4. Relational Database Model

5. Object Database Model

6. Object-Relational Database

Model

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File SystemsNo modeling techniques are applied

Data base is stored in flat files

Utilizing The structure of the operating system alone

Any searching through flat files has to be explicitly programmed

Any relationships and validation between flat files would have to be

Programmed

The capabilities is poor an dlimitede

Flat file is a simple text file, containing no structure

whatsoever

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Hierarchical Database Model

The hierarchical database model is an

inverted tree-like structure

The tables model support child-parent

relationship

Each child table has a single parent

Each parent can have multiple child

tables

Any entries in child tables can only exist

where corresponding parent entries

exist

Hierarchical database model support

one-to-many relationships

Example of a hierarchical database model

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Network Database Modelo Network database model is a refinement of the hierarchical database model

oChild tables are allowed to have more than one parent

oMany –to-many relationships are allowed in addition to one-to-many relationships

One employee can be assigned many tasks and a task can be assigned to many employee

Mangers can be a part of both departments

and companies

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Relational Database Model

Any table can be

accessed directly

without having to access

all parent objects

Any tables can be link

together regardless of

their hierarchical

structure

Any table can be linked

to both any number of

parent tables and any

number of child tables

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Relational Database Management System (RDBMS)

Software Development Kit (SDK)

End front tools Complete management kit

Example: Access

RDBMS is both the database engine and any other tools that

come with it

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The History of the Relational Database Model• The relational database model was invented by

Dr. Codd.

• The relational database began as a way of

getting a group of data from a larger data set

• This were done through a process called

normalization

• Normalization is a process which aim at

removing duplication from the data

• Normalization is composed of a number of steps

called normal forms

• The result was the Structured Query Language

(SQL)

• The development of the relational database

model was done in terms of the movement of

personal skills

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Object Database Model

Object database model provides

three dimensional structure to

data

Object database model is

efficient for finding unique items

Object database model performs

poorly for finding more than

single items

Object database model remove

the need for types and many-to-

many relationship replacement

tables

If you can figure out who little pieces work

individually, it makes the big picture

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Object-Relational Database Model

oThe Object-relational database model was created in answer to conflicting

capabilities of relational and object database models

oEssentially, object database modeling capabilities are included in relational

database

File System No database model

Hierarchical Allowing one-to-many relationships

Network Allowing for special relationships

Relational Allowing for individual element access anywhere in the database

Object Handling high-speed application of small data items within large highly complex data sets

Object-relational

Including the most accountable aspects of object database into the structure of the relational database model

Summary of the evolution of database modeling

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Examining the Types of Databases

Databases functionally fall into three categories:

Transactional

Decision support system (DSS)

Hybrid

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Transactional Databases

The primary function of the database is to add new data, change

existing data, deleting existing data

All operations are done in very small chunks, such individual

records

Examples:

•Client server database: low concurrency and low throughput

•OLTP database: enormously high levels of concurrent database

access

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Decision Support System

DSS examples:

•Data warehouse database: excessively large, OLTP is the source of

the database

•Data mart: a small subset of a larger data warehouse

•Reporting database: a data warehouse but containing only active

data ( more manageable and flexible)

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Hybrid Databases

OLTP concurrency requirements Data warehouse requirements+

A smaller hybrid database is often a more cost-effective

This section presented:

What a database does

The function of the database can determine the way in which

the database model is built

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Understanding the Database Model Design

Design process involves putting your ideas on paper before actually constructing your object

Use every thing (flowcharts, pretty picture, ERD,…) to insure that what you intend to build is not only what you need but also will actually work

Poor design can cost a company more money than it is prepared to spend

Design is needed to ensure that it works before spending humungous amounts of money finding out that it does not

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Defining the Objectives

You have to plan your steps and

you also have to know what the steps are that

you planning for

A proper relational database model should:

Aim for a well-structured database model: simple,

easy to read, easy to comprehend

Data integrity: data is not lost, destroyed when it

should be

Support both planned and unplanned queries

Each table in a database model preferably represent

a single subject or topic

Future growth must be a serious consideration

Future changes can be accommodated for

Minimize dependent between application and

database model

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Looking at Methods of Database Design

Database modeling steps:1. Requirements analysis: nature of the data, features required and

output responses2. Conceptual Design: draw pretty pictures, ERD diagrams, creation of

tables3. Logical design: Create database language commands4. Physical design5. Tuning phase: indexing, normalization, security features, ….

These separate steps are interchangeable, repeatable, iterative, and really anything

able

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Summary

In this chapter, you learned about:

The difference between a database, a database model, and an application

The hierarchical and network database models

The relational database model

The object and object-relational database models

Why different database models evolved

The relational database model is the best all round option available

Database design depends on applications

Database types

Database design objectives and methods