1 Web-Enabled Decision Support Systems Introduction to Databases Prof. Name [email protected] Position (123) 456-7890 University Name.

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Web-Enabled Decision Support Systems

Introduction to Databases

Prof. Name [email protected] (123) 456-7890University Name

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Overview

2.1 Introduction 2.2 Data, Information, and Metadata 2.3 File-Based Approach 2.4 Database Approach 2.5 Database Development Process 2.6 Data Models 2.7 Summary

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Introduction

The desire to collect, organize, and easily access information predates computer technology – Oral records

– Written records (books)

Computers, like books, have altered the way we collect, store, and retrieve information

A database is a computer solution for fast, efficient, accurate, and secure data access – Play a crucial role in the growing dominance of internet-based technology

– Used for a variety of purposes: Online shopping Driving directions Class enrollment and online grades

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Overview

2.1 Introduction 2.2 Data, Information, and Metadata 2.3 File-Based Approach 2.4 Database Approach 2.5 Database Development Process 2.6 Data Models 2.7 Summary

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Data

The term data refers to known facts that can be recorded and preserved– Include text, graphics, images, and/or video

ID Name Address City State

1 Andrew SW 16th Ave Orlando FL

2 Robert 23rd Terrace Boston MA

3 Bob 52nd Avenue Bronx NY

4 Lee Hung 52nd Avenue Albany NY

5 Richard 999 Palm Bay Detroit MI

6 Tony 15th Avenue Austin TX

Data in Context

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Information

Information is the processed data presented in a form suitable for human interpretation – The same data can be processed in a variety of ways to generate different

kinds of information

Information – Pie Chart

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Metadata

Metadata is data about data– Process of information building demands an additional description of data to

be processed

Name Data Type Size Description

ID Number 4 Unique Student ID

Name Text 50 Student name

Address Text 200 Mailing Address

City Text 50 Residential City

State Text 2 Residential State

ZIP Number 5 ZIP Code

Metadata

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Overview

2.1 Introduction 2.2 Data, Information, and Metadata 2.3 File-Based Approach 2.4 Database Approach 2.5 Database Development Process 2.6 Data Models 2.7 Summary

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Evolution of Database Systems

Two approaches to convert data to information:– File-based

Developed in 1980’s Stores, manipulates, retrieves data from large flat files

– Database (relational systems) Developed by E. F. Codd of IBM in the early 1980's Widely used today

Evolution of Database Systems

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File-Based Approach

A file is a collection of related information

A system of files and collection of application programs manipulating them is a file-based system

The University’s File-Based System

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Limitations of File-Based Approach

Efforts for query answering:– What is the average grade for Dr. John Doe’s students?

– List the activities for all students enrolled in EZZ 4162.

– Which personnel are students as well as staff?

Other limitations:– Duplication of data

– Data dependency

– Slow development, high maintenance and fixed queries

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Overview

2.1 Introduction 2.2 Data, Information, and Metadata 2.3 File-Based Approach 2.4 Database Approach 2.5 Database Development Process 2.6 Data Models 2.7 Summary

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The Database System

Limitations of file-based approach tell us that:– Parameters defining data should be separately stored– There should be a way to control and manipulate data in isolation of the

application program

A database management system (DBMS) is a piece of software that allows a user to define, create, and manage access to a database– Decouples application programs from data – The database stores all its data in one location, thereby limiting data

duplication

A database system can be defined as the combination of a database, a DBMS, and application programs

Because of the advantages offered by a DBMS, businesses and organizations prefer the database approach to the file-based approach

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University’s Database System

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Components of a Database System

There are four components in any database system:– Users

– Database application

– DBMS

– Database

Components of a Database System

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Components of a Database System (cont.)

Database:– A collection of logically related data

Database management system (DBMS):– Software that allows users to define, create, and manage database access

– Popular database management systems: Access, Oracle, IBM’s DB2, and SQL Server

Database applications: – Computer programs that allow users to manipulate the data in a DBMS

through a user-friendly interface

– Can be divided into four broad categories: Personal: Restricted to a single user Departmental: Referenced by hundreds of users over a shared system or network Enterprise: Extensions of departmental applications involving thousands of users Internet: Largest form of information sharing wherein billions of users are involved

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Components of a Database System (cont.)

Database administrator, system developer, and end user:– A database administrator (DBA) is a person responsible for all the data

resources of an organization Uses tools that come with a DBMS to improve the productivity and performance of

database planning and design

– System developers are a group of people responsible for the creation of new application programs that cater to the user requirements

Use their own tools to write programs that communicate with the DBMS

– End-users in an organization can add, update, and delete data in a database through application programs or directly through a DBMS

Use the application program to accomplish their day-to-day tasks

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Functions of a DBMS

A DBMS is primarily responsible for providing a logical view of underlying data – Allows its user to store, retrieve, and update data in the database

– Provides a clear and logical view of the process that manipulates the data

Other functionalities:– Data independence

Maintain segregation between the program and the data

– Concurrency control

– Recovery services

– Utility services Perform initialization and maintenance operations on a database

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Advantages and Disadvantages of Database Approach

Advantages:– Segregation of the application program and the data

– Minimal data duplication

– Ability to retrieve data easily

– Reduced development time and maintenance needs

Disadvantages:– Complexity

– Size

– Cost

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Overview

2.1 Introduction 2.2 Data, Information, and Metadata 2.3 File-Based Approach 2.4 Database Approach 2.5 Database Development Process 2.6 Data Models 2.7 Summary

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Database Development Process

1. Enterprise modeling:– Describes the data needed for database system

Conceptual database modeling:– Entity-relationship (E-R) modeling

1. Logical database design:– Relational data modeling is used to transform the E-R

diagram into a relational schema

2. Physical database design and creation:– Selection of software (DBMS) and hardware

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Schema

The process of database development can also be explained using schema, an overall description of the database

Three types of schemas, defined by their levels of abstraction: – External schema:

Describes the database in terms of data viewed by different users

– Conceptual schema: Describes the database in terms of entities, attributes, and relationships, along

with its integrity constraints

– Internal schema: Describes the database in terms of stored records, data fields, and indexes

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Three-Tier Architecture

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Database Development Process

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Overview

2.1 Introduction 2.2 Data, Information, and Metadata 2.3 File-Based Approach 2.4 Database Approach 2.5 Database Development Process 2.6 Data Models 2.7 Summary

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Data Models

A data model is a collection of concepts for describing data, its relationships, and its constraints– Provides a clearer and more accurate description and representation of data

– Standard platform that enables database designers and end-users to communicate

Come in three varieties: – Object-based models (conceptual schema)

– Record-based models (external schema)

– Physical data models (internal schema)

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Object-Based Data Models

Object-based data models use entities, attributes, and relationships to present information– An entity is a living or non-living object in the real world

Examples: Person, place, event

– An attribute is a property of an entity Examples: Name, address of a person

– A relationship is an association between entities Example: Register is a relationship between student and courses

Some common types of object-based data models include:– Entity-relationship data model

– Functional data model

– Object-oriented data model

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Entity-Relationship Data Model

The entity-relationship model has emerged as one of the most popular and widely used techniques in today's databases– Describes data in the form of an E-R diagram:

Entities are rectangles (“Student” and “Department”) Relationships are diamonds (“Belongs to”) Attributes are ovals (“SSN”, “Name”) Cardinalities are constraints on relationships (“>” and “|”)

Entity-Relationship Diagram

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Record-Based Data Models

Record-based data models use records to present data– A record is a structure that contains a fixed number of fields to hold a piece

of information

There are three main types of record-based data models:– Relational data models

Based on mathematical concepts of relations Use tables (or relations) to represent data and relationships

– Network data models

– Hierarchical data models

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Relational Data Models

Each table consists of a fixed number of named columns (attributes) and an arbitrary number of unnamed rows (records)

University Relational Data Model

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Transforming the E-R Data Modelto the Relational Data Model

The E-R model and the relational model are actually closely related: – Entities in the E-R model become tables in the relational model

– Attributes of in the E-R model are the table columns in the relational model

– Relationships in the E-R model are represented by a common attribute

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Overview

2.1 Introduction 2.2 Data, Information, and Metadata 2.3 File-Based Approach 2.4 Database Approach 2.5 Database Development Process 2.6 Data Models 2.7 Summary

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Summary

Data are known facts that can be recorded and preserved– Information is the processed data presented in a form suitable for human

interpretation

– Metadata is data about data

There are two approaches to convert data to information: – Traditional file-based approach

A system of files and the collection of computer programs manipulating them

– Modern database approach A database system consists of a combination of a database, a DBMS, and

application programs

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Summary (cont.)

A database is an organized collection of logically related data.

A database management system is software that allows users to define, create, and manage database access.

Database applications are computer programs that allow users to manipulate data in a DBMS through a user-friendly interface.

A database administrator (DBA) is a person or group of people responsible for all the data resources of an organization.

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Summary (cont.)

The database development process consists of four steps:1. Enterprise modeling2. Conceptual database modeling3. Logical database design4. Physical database design and creation

The process of database development can also be explained through the schema, an overall description of the database– External schema:

Describes the database in terms of data viewed by different users

– Conceptual schema: Describes the database in terms of entities, attributes, and relationships along

with integrity constraints

– Internal schema: Describes the database in terms of stored records, data fields, and indexes

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Summary (cont.)

A data model is a collection of concepts for describing data, its relationships, and its constraints– Object-based data models use entities, attributes, and relationships to

present information

– The entity-relationship data model is an example of object-based model and describes data in the form of an E-R diagram

– Record-based data models use records to present data

– Relational data model is based on mathematical concepts of relations and is an example of record-based model

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