Database Overview - software engineering

Chapter 1

Introduction to Database

Concepts

1

Concepts

Database Principles: Fundamentals of Design, Implementation and

Management, Ninth Edition, Rob and Coronel

In this chapter, you will learn:

� The difference between data and information

� What a database is, what the different types

of databases are, and why they are valuable

assets for decision making

22

assets for decision making

� The importance of database design

� How modern databases evolved from file

systems

In this chapter, you will learn

(continued):

� About flaws in file system data management

� What the database system’s main components are and how a database system differs from a file system

33

differs from a file system

� The main functions of a database management system (DBMS)

Introduction

� Good decisions require good information

derived from raw facts

� Data is managed most efficiently when stored

in a database

4

in a database

� Databases evolved from computer file

systems

� Understanding file system characteristics is

important

Why Databases?

� Databases solve many of the problems

encountered in data management

� Used in almost all modern settings involving data management:

5

� Business

� Research

� Administration

� Important to understand how databases work

and interact with other applications

Data vs. Information

� Data are raw facts, unprocessed information

� Information is the result of processing raw

data to reveal meaning

� Information requires context to reveal

6

� Information requires context to reveal

meaning

� Raw data must be formatted for storage,

processing, and presentation

� Data are the foundation of information

Data vs. Information (cont’d.)

� Data: building blocks of information

� Information produced by processing data

� Information used to reveal meaning in data

Accurate, relevant, timely information is the

7

� Accurate, relevant, timely information is the

key to good decision making

� Good decision making is the key to

organizational survival

Transforming Raw Data into

Information

88


Information (continued)

99



1010



1111

Introducing the Database

� Data Management is a discipline that focuses

on the proper generation, storage and retrieval

of data.

� Database: shared, integrated computer

12

structure that stores a collection of:

� End-user data: raw facts of interest to end user

� Metadata: data about data

� Provides description of data characteristics and

relationships in data

� Complements and expands value of data

Introducing the Database and the

DBMS (continued)� DBMS (database management system):

� Collection of programs that manages database structure and controls access to data

� Possible to share data among multiple

1313

Possible to share data among multiple applications or users

� Makes data management more efficient and effective

Role and Advantages of the DBMS

� DBMS is the intermediary between the user and

the database

� Database structure stored as file collection

� Can only access files through the DBMS

� DBMS enables data to be shared

1414

� DBMS integrates many users’ views of the data

� End users have better access to more and

better-managed data

� Promotes integrated view of organization’s operations

� Probability of data inconsistency is greatly reduced

� Possible to produce quick answers to ad hoc queries


(cont’d.)� Advantages of a DBMS:

� Improved data sharing

� Improved data security

� Better data integration

15

� Better data integration

� Minimized data inconsistency

� Improved data access

� Improved decision making

� Increased end-user productivity

15


(continued)

1616

Types of Databases

� Databases can be classified according to:

� Number of users

� Database location(s)

� Expected type and extent of use

17

Expected type and extent of use

� Single-user database supports only one

user at a time

� Desktop database: single-user; runs on PC

Types of Databases (continued)

� Multiuser database supports multiple users

at the same time

� Workgroup and enterprise databases

� Workgroup:

1818

� Workgroup:

� Multi-user database that supports a small group of users

or a single department

� Enterprise:

� Multi-user database that supports a large group of users

or an entire organization


Can be classified by location:

� Centralized:

� Supports data located at a single site

� Distributed:

1919

� Distributed:

� Supports data distributed across several sites


Can be classified by use:

� Transactional (or production):

� Supports a company’s day-to-day operations

� Data warehouse:

2020

Data warehouse:

� Stores data used to generate information required to make tactical or strategic decisions

� Often used to store historical data

� Structure is quite different

Types of Databases (cont'd.)

� Unstructured data exist in their original

(raw)state – unable to be processed

� Structured data result from formatting

� Structure applied based on type of processing to be performed – generate information

21

be performed – generate information

� Semistructured data have been processed

to some extent – e.g. webpage, email etc

� Extensible Markup Language (XML) represents data elements in textual format

� XML database supports semistructured XML data

22

2323

2424

Why Database Design Is Important

� Database design focuses on design of

database structure used for end-user data

� Designer must identify database’s expected use

� Well-designed database:

25

� Well-designed database:

� Facilitates data management

� Generates accurate and valuable information

� Poorly designed database:

� Causes difficult-to-trace errors

25

Evolution of File System Data

Processing� Reasons for studying file systems:

� Complexity of database design is easier to understand

� Understanding file system problems helps to avoid

problems with DBMS systems

Knowledge of file system is useful for converting file

26

� Knowledge of file system is useful for converting file

system to database system

� File systems typically composed of collection of

file folders, each tagged and kept in cabinet

� Organized by expected use

26


Processing (cont'd.)

� Contents of each file folder are logically related

� Manual systems

� Served as a data repository for small data collections

� Collection of file folders kept in file cabinet

Organization within folders based on data’s expected use

27

� Organization within folders based on data’s expected use (ideally logically related)

� System adequate for small amounts of data with few reporting requirements

� Finding and using data in growing collections of file folders became time-consuming and cumbersome

� Designed the application programs

27


Processing (cont'd.)

� Initially, computer file systems

resembled manual systems

� Computerized file systems

28

Computerized file systems

� Data processing (DP) specialist converted

computer file structure from manual system

� Wrote software that managed the data

28

Historical Roots: Files and File Systems

(continued)

2929

Historical Roots: Files and File

Systems (continued)

3030


(continued)

3131

Historical Roots: Files and File

Systems (continued)

� As number of databases increased, small file

system evolved

� Each file used its own application programs

3232

� Each file was owned by individual or

department who commissioned its creation


(continued)

3333

Problems with File System

Data Management� Every task requires extensive programming in a

third-generation language (3GL)

� Programmer must specify task and how it must be done

3434

� Modern databases use fourth-generation

languages (4GL)

� Allow users to specify what must be done without specifying how it is to be done


Data Management

3535

Problems with File System Data

Processing� File systems were an improvement over manual

system

� File systems used for more than two decades

� Understanding the shortcomings of file systems aids in

development of modern databases

36

development of modern databases

� Many problems not unique to file systems

� Even simple file system retrieval task required

extensive programming

� Ad hoc queries impossible

� Changing existing structure difficult

36

Problems with File System Data

Processing (cont'd.)� Security features difficult to program

� Often omitted in file system environments

� Summary of file system limitations:

� Requires extensive programming

37


� Cannot perform ad hoc queries

� System administration is complex and difficult

� Difficult to make changes to existing structures

� Security features are likely to be inadequate

37

Structural and Data Dependence

� Structural dependence: access to a file is

dependent on its own structure

� All file system programs must be modified to conform to a new file structure

38

� Structural independence: change file

structure without affecting data access

� Data dependence: data access changes

when data storage characteristics change

� Data independence: data storage

characteristics do not affect data access38


Data Management� Time-consuming, high-level activity

� As number of files expands, system

administration becomes difficult

� Making changes in existing file structure is

3939

� Making changes in existing file structure is

difficult

� File structure changes require modifications

in all programs that use data in that file

Data Redundancy

� File system structure makes it difficult to

combine data from multiple sources

� Vulnerable to security breaches

� Organizational structure promotes storage of

same data in different locations

40

same data in different locations

� Islands of information

� Data stored in different locations is unlikely

to be updated consistently

� Data redundancy: same data stored

unnecessarily in different places

40

Data Redundancy (cont'd.)

� Data inconsistency: different and conflicting

versions of same data occur at different

places

� Data anomalies: abnormalities when all

41

� Data anomalies: abnormalities when all

changes in redundant data are not made

correctly

� Update anomalies

� Insertion anomalies

� Deletion anomalies

41

Data Redundancy

Types of data anomalies:

� Update anomalies

� Occur when changes must be made to existing records

4242

records

� Insertion anomalies

� Occur when entering new records

� Deletion anomalies

� Occur when deleting records

Database Systems

� Problems inherent in file systems make using

a database system desirable

� File system

� Many separate and unrelated files

4343

� Many separate and unrelated files

� Database

� Logically related data stored in a single logical data repository

Database Systems

4444

The Database System Environment

� Database system: defines and regulates the collection,

storage, management, use of data

� Database system is composed of five main parts:

� Hardware

� Software

4545

� People

� Procedures

� Data


(continued)

4646


(cont'd.)� Hardware: all the system’s physical devices

� Software: three types of software required:

� Operating system software

� DBMS software

47

� DBMS software

� Application programs and utility software

47 Database Systems, 9th Edition


(cont'd.)� People: all users of the database system

� System and database administrators

� Database designers

� Systems analysts and programmers

48

� Systems analysts and programmers

� End users

� Procedures: instructions and rules that

govern the design and use of the database

system

� Data: the collection of facts stored in the

database48 Database Systems, 9th Edition

DBMS Functions

� DBMS performs functions that guarantee

integrity and consistency of data

� Data dictionary management

� defines data elements and their relationships

4949

� Data storage management

� stores data and related data entry forms, report

definitions, etc.



DBMS Functions (continued)

� Data transformation and presentation

� translates logical requests into commands to

physically locate and retrieve the requested data

� Security management

5252

� enforces user security and data privacy within

database


� Multi-user access control

� uses sophisticated algorithms to ensure multiple

users can access the database concurrently

without compromising the integrity of the

database

5353

database

� Backup and recovery management

� provides backup and data recovery procedures

� Critical to preserving database’s integrity


� Data integrity management

� promotes and enforces integrity rules� Minimizes redundancy

� Maximizes consistency

Database access languages and application

5454

� Database access languages and application programming interfaces

� provide data access through a query language

� Database communication interfaces

� allow database to accept end-user requests via

multiple, different network environments


5555

5656


5757

Managing the Database System:

A Shift in Focus� Database system provides a framework in which

strict procedures and standards enforced

� Role of human changes from programming to

managing organization’s resources

Database system enables more sophisticated

58

� Database system enables more sophisticated

use of the data

� Data structures created within the database and

their relationships determine effectiveness


Managing the Database System:

A Shift in Focus (cont'd.)� Disadvantages of database systems:

� Increased costs

� Management complexity

� Maintaining currency

59

� Maintaining currency

� Vendor dependence

� Frequent upgrade/replacement cycles


Summary

� Data are raw facts

� Information is the result of processing data to

reveal its meaning

� Accurate, relevant, and timely information is

60

� Accurate, relevant, and timely information is

the key to good decision making

� Data are usually stored in a database

� DBMS implements a database and manages

its contents


Summary (cont'd.)

� Metadata is data about data

� Database design defines the database

structure

� Well-designed database facilitates data

61

� Well-designed database facilitates data management and generates valuable information

� Poorly designed database leads to bad decision making and organizational failure

� Databases evolved from manual and

computerized file systems


Summary (cont'd.)

� In a file system, data stored in independent

files

� Each requires its own management program

� Some limitations of file system data

62

� Some limitations of file system data

management:


� System administration is complex and difficult

� Changing existing structures is difficult

� Security features are likely inadequate

� Independent files tend to contain redundant data

� Structural and data dependency problems62 Database Systems, 9th Edition

Summary (cont'd.)

� Database management systems were

developed to address file system’s inherent

weaknesses

� DBMS present database to end user as

63

� DBMS present database to end user as

single repository

� Promotes data sharing

� Eliminates islands of information

� DBMS enforces data integrity, eliminates

redundancy, and promotes security


The End

64

The End

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Database Overview - software engineering

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