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INFORMATION SYSTEMSBy: M Rafeeq

Chapter- II

DATABASE MANAGEMENT SYSTEMS

Father of Database ----- C.J. DatePurpose: This is to know how data resources are managed and how to provide shared

access to the data in information systems.

I. Introduction: -

The primary role of Information Systems is to collect data and make it available tomanagers throughout the company. Data collection is a fundamental step in transactionprocessing.

Right information and right Information systems are the mantra for success inmodern day business. Every organization maintains the information it needs in any of the

following forms: By manual means, computerfile structures and in the form ofdatabases.

Information maintenance through manual means has practically disappeared and withthe advancements in computer hardware and soft ware, dependence on computer systems

has become so crucial

Data Management integrates the divisions of a company, supports team work andhelps to control the organization.

nn

Fig.: -With out DBMS Fig.: - With a DBMS

(Integrated data with shared access)

Without DBMS, data will be scattered through the company, making difficult to share

the information, due to this data inconsistency, duplication and errors occurs.

With DBMS, it maintains data through a common interface. So, data definition,

access, consistency and security are maintained by the DBMS.

1

Strategy

Tactics

Data files

Operations

Strategy

Tactics

O erations

DBMS

Databas

e

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The concepts ofDatabase and Database Management were developed to solve the

problems offile processing system.A Database is an integrated collection of logically related records and files. It

consolidates all records previously stored in independent files, which serves as common

pool of data to be accessed by many different application programs.

Database Management involves the control of how databases are created,interrogated and maintained.

Databases are typically supported and managed through software known as

Database Management System (DBMS).

DBMS are designed to deal with multiple users at the same time. DBMS are one ofthe most important tools in Management Information Systems (MIS). The overall design

(structure and data) is maintained and controlled by the DBA (Database Administrator).

Fig.: - MIS people and databases

II. File Structures: -A file is a collection ofrecords. Storing of records on magnetic media is called the

file structure.

a) Data stored in papers-based, Manual filing system: -

b) Data stored in Computer-based, Electronic filing system: -

2

DBA

Database

Management

System

Data

(Standards designand control)

Program Program

Programmer/

Analyst

Computer

Computer

ComputerComputer

ManagersAd hoc queries

and reports

Data collection

and transaction

processing

Business operations

Characters Data element Records Files.

Binary digits Characters Data element Records Files.(Bits) (Bytes)

0 10101011 10101010010001

Business

needs

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Methods (Models) of a File Structures: -

Records should be organized in a file, in such a way that it provides quick access to

the desired record forretrieval, updating and saving.The basic models of file structures are as follows:

1.Sequential file structures.

2.Direct file structure.

3.Indexed sequential file structure.

1. Sequential File Structure: -

In this model records will be stored in sequentially using a Primary key (Rollno., Employee Id. no.). The records will be arranged in ascending ordescending order

based upon the key attribute in the record. The sequence of records in the file can be

changed by sorting the file.

E.g.-With a sequential access to retrieve an employee record with an ID number2500 is done by scanning all the records sequentially between 0001 and 2500 records.

. Sequential access can be fast and inexpensive, if files are stored in batch

processing mode. The transactions leading to changes in the file data are collected in abatch periodically.

E.g.: - Transfers, Promotions, and Retirement which lead to changes in the

personal file data can be collected on a monthly basis. These transactions are collectedin a batch are then record in the form of a transaction file, which is arranged in a

sequence as the master file to be updated. The updating involves reading of records

from both transaction and Master file.

The additions, deletions and changes are carried out in the records of the master

file and updated records are written on a new updated master file.

3

Old

Maste

rfile

Transa

ction

file

New

Maste

r

file

Update

To maintain

accurate and current

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2. Direct file structure: -

In this method records are stored randomly i.e., not in sequence order by primarykey.

In direct access a hashing technique orrandomizing is applied to primary key.

Hashing technique is used to generate storage address of records in the file.There are many number of ways to convert a key to a numeric value. The keys

may be numeric, alphabetic oralphanumeric.Using hashing technique and storing the data on a direct access medium, retrieving

of records are done directly.

E.g.: - To retrieve an ID number of employee 2500, it can be retrieved directly

instead of scanning all the records from 0001 to 2499.

Disadvantages: - Several record numbers may generate the same address. Handling

this problem exits ----- but requires special processing, which slow down the storage

and retrieval of records.

3.Indexed sequential file structure: -

In this method records are stored sequentially on a direct access medium with aspecific address for each record.

An Index is maintained as records are added to the file and it keeps track of disk

address of each record. This method is called Indexed Sequential Access Method(ISAM). This method permits both sequential and direct access of records in a file.

Accessing Records: -

Records are stored to access in the following ways:

1) Adding new records to a file2) Deleting record from a file

3) Modifying records in a file

4) Viewing records from a file on a screen.5) Creating reports from records in a file.

III. Database concepts: -

A file is a collection ofrelated records. A Database is a collection ofrelated files.

4

Index

Primary key Disk address

3548 8455283549 853658

3550 861788

Binary digits Characters Data element Records Files Database(Bits) (Bytes) (Field)0 10101011 10101010010001

A collection

of related

files

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In traditional, firms computerized their operations on an application-by-application

basis, where records in an each file were designed specially for each application.

E.g.: - 1) Computerized pay rolls.

2) Computerized Order processing

1). Data Independence: -

Programs lack data independence i.e., at any time the record format of a file ischanged [E.g.: - a field was dropped, added or modified] and every program, which

accesses that file, had to be changed.

Def.: - The ability to define or describe data separately from an application

program. [Defining data separately from the programs is called data independence]

Advantage:-It is possible to change the data without having to change the programs.

2). Data Redundancy: -

Def.: - When the same value in the same data element describing the same entity andoccurs in more than one file.

E.g.: - Student file in Enrollment office

Student file in Placement officeStudent file in library

Multiple files lead to data redundancy and data inconsistency.

3). Data Consistency: -

Change of address made at one office i.e., Placement office, to ensure thatthey send notices to the right location. But in other offices addresses are not changed

(incorrect), which leads to data inconsistency.

In accuracy in data files, such as inconsistencies, mean that files lack dataconsistency.

Office may use separate programs to process their files.

Like Enrollment office may run -- COBOL program to access its record.Placement office may run -- an Assembler language program to access its record.

[Compilers and Assemblers are translation programs, for translating user

programs in to machine language programs].

IV. Components of DBMS: -

Database Management Systems is a collection of software programs, whichperforms the following functions:

1. Stores data in a uniform and consistent way.

2. Organizes the data into records in a uniform and consistent way.3. Allows access to data in a uniform and consistent way

DBMS is purchased from commercial vendors. The components of a DBMS will

vary from one vendor to vendor.1) Data dictionary/directory

2) Data language

3) Tele processing monitors4) Application development tools

5) Security software.

5

6) Archiving, Backup and Recovery systems

7) Report writers

8) Query language (SQL, QBE)9) Multi platform databases

10 Web servers software.

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1) Data dictionary: - [Major tool of dba]It is a software module and database containing meta-data i.e., data about

data. Data dictionary contains Meta -data about the structure, data elements and other

characteristics of an organizational database.It contains names and descriptions of every data element in the database and

also contains how data elements relate to one another.The data dictionary contains schema of the database. It describes each data

item in the database, lists its structure, source, person, authorized to modify it, etc.

Through Data dictionary, a DBMS stores data in a uniform and consistent

manner thus reducing redundancy.

2) Data languages: -

DDL (Data Definition Language) -- This is to describe the characteristics of the

data elements. (Standard commands ---- uniform). These commands are part ofDML

(Data Manipulation Language), where programmers use to retrieve and process data

from the database.

DML commands ---- Get, Find, Insert

3) Teleprocessing monitors: -

It is a communication software package, which manages communicationbetween database and remote terminals.

TPMhandles order entry systems.TPM can also be developed by DBMS software firm and offer a companion

packages to their db.

4) Application Development tools: -

It is a program designed to help programmers to develop application programs

that use the db.Application development programs included in DBMS products often include

in CASE (COMPUTER AIDED SOFTWARE ENGINEERING) tools.

5) Security software: -

It is to protect the db from unauthorized access and from unauthorized viruses.

6) Archiving, Backup and Recovery systems: -

Archiving program provide db manager with tools to make copies of the

database, which can be used, when original database records are damaged ordestroyed.

Recovery/Restart systems are tools used to restart the db and to recover thelost data in the event of a failure.

Backup system automate making copies of data & work with restart /recovery

systems to recover from db failures.

7) Report writers: -

It is used to design output reports without writing an application program in

programming language-COBOL.

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8) Query languages: -

It is to retrieve data from db.It is a set of commands used to access data from a database. It allows to ask ad

hoc questions interactively.

Tools used to query a db: -

a) SQL (Structured Query Language): -English like commands. It used in most DBMS.E.g.: - Select NAME from EMP, where NAME=Raj;

b) Natural language Quires: -

These are structured so that the commands used are as close to StandardEnglish as possible.

E.g.: - List the names and address of all customers who live in Ashok Nagar.

c) QBE (Query By Language): -It does not require writing statements directly. It uses graphical approach to

construct a query. Drag and drop of data element from the records is done.

9) Multiple Platform Database: -

Some DBMS software products work on many different computer hardwareand operating system platforms.

E.g.: - DBMS - offers in versions for mainframe, mini computers, workstations

and microcomputers.

10) Web server software: -

Many DBMS vendors have integrated WWW sever software into their

products.

Database Web server enables users with web connectivityto access the data from where ever they are located.

VI. Models of DBMS: -

There are four models to organize record and their relationships in a database.

Hierarchical database modelNetwork database model.

Relational database model

Object oriented database model.

1) Hierarchical Database Model: -In this model records are organized into a hierarchy of relationships like an

inverted tree pattern (tree with branches turned upside down).

The relation between entities are structured in such a way as to link with only

one data item at the high level (1: M relationship)-called Parent-child relationship.

Data stored in a lower level node called child record can be accessed onlythrough the high level node called parent record.

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Fig.: - Hierarchical database model

2) Network Database Model: -

In this model, the relationships are stored in the form of sets; each set having

one owner record and one or more number records.This structure permits multiple relations between data items (M:M relation ship)

Any data element can be related to any number of other data elements

Fig.: - Network database model

3) Relational Database Model: -

In this model all data elements stored in the database are organized in tables.

Different data tables are linked up using common type of data items in a table. The

table is called relation. The columns of the table are called domains and the rows ofthe table are called Tuple.

Tuple contains data items called data elements.

4) Object-Oriented Database Model: -

In this model each object is bound together with its own data and set ofinstructions that describes the behavior and attributes of the object.

The object use messages to interact with one another.

Every object is described by set of attributes.

8

Building1

Room 2Room 1

Equipment 3Equipment 2Equipment 1

Vendor 3Vendor 2Vendor 1

Repair 3Re air 2Re air 1

Parent of room

Children of Building

Parent of Equipment

Children of Room

Parent of Vendor

Children of Equipment

Parent of Repair

Children of Vendor

Vendor 1 Vendor 2

Re air 3Re air 2Re air 1

E ui ment 2E ui ment 1

RELATION1 (PRIMARY KEY, ATTRIBUTES.)

RELATION2 (PRIMARY KEY, FORIEGN KEY, ATTRIBUTES.)

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Fig.: Object-oriented database model

Evolution of Database Structure: -

5th Generation ---- Object oriented structures4th Generation ---- Relational structures.

3rd

Generation ---- Network structures.2nd Generation ---- Hierarchical structure1st Generation ---- File structures

V. Views of the data: -

Any database contains two types of data

1) Actual data-employee names, hourly wage rates and hours worked

2) Information about data. i.e., it contains

a) Definition of each data elementb) How data element relates to other data elements.

Data that describe the properties or characteristics of other data is called Meta data.

Data in a database has two levels.

1) Logical view: -

It is the way where users perceive records are structured and their relationship among the records in the database.

2) Physical View: -

The way the records are actually organized and stored.

9

Object Class 1

Attributes

Methods

Object Class 1

AttributesMethods

Object Class 1

Attributes

Methods

User view 1

(Report)

User view 2

(Screen display)

User view 3

(Transaction)

Conceptual

view

Physical

viewInternal schema

Conceptual

Schema

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A schema is a description of the logical view of the database. It includes all

the data elements in the databases and shows how these elements are logically relateto each other. Tools used to design schema is an E-R diagram.

A Sub schema is a less compressive logical view of the database .It consists

of subset of data elements in a database by an application programmer, anapplication program or a user. Subschema makes the database secure i.e., DBMS

will not allow users of an application program to access data not set their view.

VII. Advantages of DBMS: -

1) Data sharing : -Database permits simultaneous multiple access to the database i.e., multiple

users can share the same data.

2) Redundancy control: -

Database minimizes duplication of data from file to file. This is avoided by

maintaining only one record in a database rather than in the files of manydepartments.

3) Reduced data consistency : -

Reduced redundancy means data consistency is also reduced.4) Data independence : -

The data is logically designed in to databases and it is independent ofapplications. Since the data is program independent and, any application can use itwithout any modification to the code (reduces program maintenance costs).

5) Data availability : -The database is centrally controlled and access to data is permitted through

an authorization schema. The data resources are therefore available to the user in theorganization, subject to authorization procedure.

6) Increased user productivity : -

Data is used by query languages and report generators allow them to

produce reports without any help from MIS people, which allow to complete the workfast.

7) Improved Data administration and control : -

Data dictionary became easier to control so accessing, privacy, updations and

deletions are also made easier control, because the database responsibility is under the

control of one person or department.

VIII. Problems Of DBMS: -

1) Concurrency Problems : -

When DBMS is not designed for multiple users the following problems occursE.g.: - Sales person A Sales person B

Customer A - 200 Customer B 150

a) File locking Only one sales person can sell product any time.

b) Record locking- Unavailable for use for another people.

c) Field locking- it allows only one person to make a change in data element.

Another method to solve concurrency:

Versioning - It permits every user to view a record and make updates in that record.

This system checks the record before updations is actually done.

10

But in inventory

there are only 300

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2) Resource Problems : -

DBMS requires Extra computing resources. Data must be stored online toanswer queries, which requires:

- Additional hard disk

- More communication devices- Database

- Increase in size of CPUs

3) Security Problems : -Only authorized personnel should access data and only these persons can add,

update and delete in the database.

So for better security of data Login identification and Passwords are used

IX. Normalization: -

Normalization is an important technique to design databases. It is primarily a tool tovalidate and improve a logical design, so that it satisfies certain constraints that avoid

unnecessary duplication of data.

DBMS is a powerful tool, with ability to present data in many ways. They are used bymanagers to answer many different types of questions. This flexibility is not automatic so

databases need to be carefully designed. Poor design leads to unnecessary duplication of

data.

Normalization is the process ofgathering data items (or properties) into smaller

well-structured relations. Normalization reduces the complexity of data structure and

makes it as simple as possible for effective management and manipulation.

Normalization is the process of converting a relation to a standard form.A table is said to be in a particularnormal form if it obeys the rules of that normal

form.

The process of normalization starts with the normalized data.

1) First Normal Form (1NF) : -The process of 1NF is to be done as follows:

1. The unnormalized data is converted into a tabular form.2. All the columns and rows in the table are filled.

3. Repeated occurrences of data items are removed.

4. The keys to the entire table are identified.

In writing a database repeating section should not be present. So, that space canbe saved. When a table contains no repeating sections, we say that it is a firstnormalform. [Or a relation, which contains no multivalued attributes]

11

TransID Rentdate CustID Name Phone Address VideoID Copyno Title Rent

1 16/03/2001 5 Ramu 7610052 Koti 3 1 PTKK 20

1 16/03/2001 5 Ramu 7610052 Koti 4 2 KNPH 20

2 18/03/2001 6 Shiva 6318040 Abids 3 2 PTKK 20

2 18/03/2001 6 Shiva 6318040 Abids 6 1 HSSH 20

2 18/03/2001 6 Shiva 6318040 Abids 2 1 MKKH 20

3

3

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Rent(TransID, Rentdate, CustID, Name, Phone, Address, (VideoID, Copyno, Title, Rent))

Rent1(TransID, Rentdate, CustID, Name, Phone, Address)

Rent2(TransID, VideoID, Copyno, Title, Rent)

Rent1

Rent2

2) Second Normal Form (2NF) : -The process of 2NF is to be done as follows:

1. Using the table of 1NF, identify those items that are dependent on theentire key and those are partially dependent on the entire key.

2. Split the tables into smaller tables in such a fashion that each item depends

only on the entire key.

Rent2(TransID, VideoID, Copyno, Title, Rent)

Videosrented(TransID, VideoID, Copyno) Video(VideoID, Title, Rent)

3) Third Normal From (3NF) : -

12

TransID Rentdate CustID Name Phone Address

1 16/03/2001 5 Ramu 7610052 Koti

2 18/03/2001 6 Shiva 6318040 Abids

3 18/03/2001 4 Raj 5348672 S.R Nagar

4 16/03/2001 5 Ramu 7610052 Koti

TransID VideoID Copyno Title Rent

1 3 1 PTKK 201 4 2 KNPH 20

2 3 2 PTKK 20

2 6 1 HSSH 20

2 2 1 MKKH 20

3 1 1 KKHH 203 9 1 KMKK 20

TransID VideoID Copyno

1 3 1

1 4 2

2 8 2

2 6 1

2 2 1

3 1 1

3 9 1

VideoID Title Rent

1 KKHH 20

2 MKKH 20

3 PTKK 20

4 KNPH 20

6 HSSH 20

9 KMKK 20

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A relation that is in Second normal form and has no transitive dependencies

present.Transitive dependency ---- a functional dependency between two or more nonkey

attributes.

[The table must already be in second Normal Form. Customer data is entered foreach and every new transaction, where it does not depend on the Primary Key (Trans

Id), But it depend on the Customer Id column].Rent1(TransID, Rentdate, CustID, Name, Phone, Address)

Rentals(TransID, Rentdate, CustID) Customers(CustID, Name, Phone, Address)

111ksdcndlkncv 1

X. Specialized databases: -

In addition to traditional databases many organizations have developed specializeddatabases.

1) Intranet and Hypermedia database

2) On line database3) Data warehousing

4) Data Marts

5) Online Analytical processing6) Image databases

7) Document database.

Decision makers to make decisions require internal and external data to reduce riskand increase competitiveness.

1) Hypermedia databases and Intranet : -Hyper text document s are contains link to other pages.

13

TransID Rentdate CustID

1 16/03/2001 5

2 18/03/2001 6

3 18/03/2001 4

4 16/03/2001 5

CustID Name Phone Address

4 Raj 5348672 S.R Nagar

5 Ramu 7610052 Koti

6 Shiva 6318040 Abids

Customers

Name

Phone

Address

Rentals

TransID

Rentdate

CustID

Videosrented

TransID

VideoID

Co no Video

VideoID

Title

Rent

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Hypermedia databases are systems in which hypertext documents are the

records. The documents in hypermedia databases can be internal and external.The external documents located at more than one site, by World Wide Web.

The web is the part of interconnected computer systems called the Internet.

The internal documents are available on companys own network referred toas intranet.

Hypermedia can be text, image, sound clips, video clips and other types ofdata, which can be read by a single piece of soft ware called a browser.

Information stored in hypermedia documents may be accessed in non-

sequential fashionby just clicking a mouse button to link the other documents.

Any Browser can read any hypermedia document as it is written in a standard

format called HTML (Hyper Text Markup Language) in the form of tags.Documents formatted in HTML can be read by any browser on any platform i.e.,

Macintosh, IBM PC or a UNIX workstation.

2) On-Line databases: -

Managers can access information directly from on-line databases through on-

line information services such as Microsoft Network (MSN), America Online(AOL), etc.

On-line databases are essentially electronic libraries, where different types of

information can be available when connected to World Wide Web.

3) Data warehousing: - [Creates enterprise wide]

A system that stores, retrieves, manages or manipulates massive amounts of

data that may be from the organizational databases and external sources. The data istypically stored in one large file server or a central computer.

The warehouse of data is often separated from organizations production

databases so that users can use this resource with out reducing the response time for

an organization routine data processing operations.Traditional databases are transaction orientedData warehouse is subject oriented.Purpose of data warehouse: -To make large amount of data available to

organization personnel to support in decisions. The key to a successful warehouse is

to integrate companies and external database systems.

Major components:

1) Data

2) Hardware and network infrastructure that provides storage andaccess.

3) Software to extract data4) Graphical query tools5) A user guide (Help)

6) Warehouse Management soft ware for Information system

personnel to maintain and upgrade the warehouse.7) It is a generation of technologies that provide multidimensional

views of database, so refers to as multidimensional analysis.

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4) Data Marts: -

Data marts are formed to meet data needed for one department in anorganization.

These are built faster and easier than data warehouse because they focus on the

subset of an organizations data needs.

5) OLAP [On-Line Analytical Processing]: -It is a group of technologies that provide multidimensional views of a database, soreferred to as multidimensional analysis.

It permits to ask ad hoc questions of an OLAP database for tactical and strategic

planning decision support.

OLAP databases are data warehouses that may include filtered and aggregateddata from many sources (Internal, external)RDBMS stores data in two-dimensional tables like a spreadsheet.OLAP stores data in multi dimensional. Data stored in this way is called a

hypercube.

Data Mining: It helps business to find meaning in data lying idle. It helps in drawinginferences from the data and in understanding the customer, products and markets

better.

Data Mining employs a host of techniques, i.e., statistical techniques like linearprogramming, data analysis, machine learning and online analytical processing.

6) Image databases: -

Image management software is used to store images in an image database inorder to find and access the data quickly.

Multimedia, CAD/CAM, presentation graphics etc are used to create images.

7) Document databases: -Document databases consist of data in the form of letters, memos, reports and other

documents in an organization. Document management software allows easy access,and manipulates the documents wherever they are located.

The document databases can be compressed in order to reduce the disk space.

XI. Distributed systems: -

The key component to the success of many organizations is to network an

organization.This is to connect to theircustomers and vendors.

Distributed processing: -

It is defined as a system in which both computer power and data occur at more than

one site, and application programs are run at more than one site.

It is associated with all types of network.E.g.: -LANs, WANs, and even Internet Geographically distributed.

15Networ

kRouter

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Workstations Workstations

Hub: -A device that connects many workstations to a Network.

Reasons for Implementing Distributed Processing: -Distributed data processing became uneconomical, because of centralized computer

systems.

a) Improved Response time: - But if more people logon the response time here also

reduces. E.g.: - 8AM to 11AMb) Reduced costs: - Transmission costs are reduced.

c) Improved accuracy and concurrency: - control of data entry and data storage.

d) Reduced mainframe costs.

e) Smother growth: - No need to install, program debugged and data conversion.f) Increased reliability: - In centralize system, if host fails entire system will fail. In a

distributed system, failures of one processor disrupts only the operations depend on the

processor.g) Resource sharing: -Many users can share and locate at any where on the network.

h) Increased user satisfactions:-In centralized application, program development staff

usually face a large backlog of application development tasks.

Distributed databases: -

When organizations need to decentralize their computer processing, they also need todecentralize their databases, called distributed database systems.

There are two types of distributed databases.

1) Replicated dbs and 2) partitioned dbs

1) Replicated dbs : -

This provides duplicates of all data at all sites, but at every location same data willbe accessed.

16

Host 1 Host 2 Host 3

Hub Hub Hub

Fig: - Geographically distributed processing Fig: - Locally distributed processing

Networ

k

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Advantage: -Security to the database in case of failure at one location.

Disadvantages: -1) Very Expensive

2) Difficult and costly to maintain for each data element.

2) Partitioned databases: -

In this the db is divided in to segments, which are appropriate to certain

locations and distributed only those locations.E.g.: -1) Database can be partitioned functionally i.e., financial, marketing and

administrative data can be kept at corporate head quarters. Relevant production and

personnel data can be kept at each manufacturing plant and office site.

2) Database can be partitioned geographically i.e., all locally relevant information -financial, marketing, administrative, production and personnel.

Advantages of Distributed dbs: -

1) Reducing costs, transferring data between remote sites and its head quarters

2) Provides faster response time i.e., filling ordering, answering requests.

Disadvantages: -

1) Additional files and databases are established, so creates redundancy and

inconsistency.

Client/Server computing: -17

dbdb

Workstations

(Chennai)

Workstations

(Banglore)

(Copy 1)(Copy 2)

dbdb

WorkstationsHead quarters

Workstations

Factory

Copy 1Copy 2

Network

db

Workstations

Factory

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Client - PC Application processing.

Server - LAN (mini/micro) - Makes a requests.

Components for hardware side: -

1) Server, 2) client 3) a good communication system.

Components for software side: -1) A good GUI based OS 2) DBMS 3) Necessary Open Data Base Connectivity

(ODBC) drivers and Application Programming Interface (API).

1) SQL servers : -Common application of client /server computing is use of relational database

software called SQL server. This package usually runs on a network. These aremore reliable than LAN based.

2) Downsizing : -

It reduces equipment cost, development cost, purchasing, hardware andsoftware maintenance.

Inter organizational IS: -Information System is confined to organizational boundaries.

E.g.: - Accounting IS ------ To employees of accounting.

Now it is distributed to more than one called Inter organizational IS ---

client/Server technology.

1) EDI (Electronic Data Interchange) ----- primarily bilateral

2) Electronic Market System ----- Multilateral

Data Dictionary: -

The data dictionary is the heart of the database, which holds all information

about the data stored in the database. Both Management and System peopleextensively use data dictionary for various functions. It acts as a catalogue providing

information on the following:

1. The way data is defined2. Types of data that are present

3. Relationship among various data entities.

4. The representation format.5. Keys for the database.

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6. People who are accessing the data.

7. Access rules for every user.

Primary key:

An attribute (or combination of attributes) that uniquely identifies each row ina relation.

Secondary key:One field or a combination of fields for which more than one record may have

the same combination of values.

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