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Information SystemAn Information system comprises all thecomponents such as hardware, software,

communication systems that collect, manipulateand distribute data or information.

Component

Hardware

Software

Communication system

Data1


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Information system in business

In business environment IS typically supportbusiness processes and operations, decisionmaking and competitive strategies.

Aim: To make organization more productiveand profitable and to gain competitiveadvantage

Transaction processing system(TPS)Management Information system(MIS)

Executive Information system(EIS)

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Contd..

Decision support system(DSS)

Expert system(ES)

Strategic Information System(SIS)Customer relationship management system

Enterprise resource planning systems

Office automation systemsDecision support system

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Data VS Information

What is data?

Data can be defined inmany ways. Information

science defines data asunprocessed information.

Collection of raw data.

Unstructured does not

have context and may notbe relevant to thereceiver.

What is information?

Information is data that

have been organized andcommunicated in a

coherent and meaningfulmanner.

Data is converted intoinformation, and

information is convertedinto knowledge.

Knowledge; informationevaluated and organized sothat it can be used

purposefully. 4


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Contd..

Data Information Knowledge Action

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Open VS Close System

An open system is acollection of interacting software,

hardware and humancomponents.

It is designed to satisfythe stated needs.

It contains componentswith interfacespecifications that arefully defined.

A closed system is asystem that resists theinclusion and integrationof new ideas.

Not adopting new andfeasible ideas, a closesystem doesnt serve the

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Information quality attribute

Software quality is the degree to which thesoftware possesses a desired combination of thefollowing attributes:

Performance- is the degree to which a system orcomponent accomplishes its designated functionswithin the given constraints such as speed,accuracy etc.

Dependability-reliance of the service it provide.It is concerned with the occurrence of thefailure.

(8 September 2010- Second Lecture)

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Contd..

Security- complete freedom from danger i.eprotection of the system data againstdisclosure, modification or destruction.

Safety it is concerned with the occurrenceof the accidents.

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What is a database?

A database is any organized collection of data.

A collection of related pieces of data:

Representing/capturing the information about areal-world enterprise or part of an enterprise.

Collected and maintained to serve specific datamanagement needs of the enterprise.

Activities of the enterprise are supported by thedatabase and continually update the database

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DBMS

Defined as a collection of interrelated dataand a set of programs to access the data.

A Database Management System (DBMS) is asoftware package designed to store andmanage databases.

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Contd..

A database management system (DBMS) suchas Access, FileMaker, Oracle or SQL Serverwhich provides the software tools to organizedata in a flexible manner. It includes tools toadd, modify or delete data from the database,ask questions (or queries) about the data

stored in the database and produce reportssummarizing selected contents.

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Advantages of DBMS

Control of data redundancy

Data consistency

More information from same amount of data.Sharing of data

Improve of security

Improve of data integrityImprove data accessibility and responsiveness

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Disadvantage

Complexity

Size

Cost of DBMS

Additional hardware cost

Performance

Higher impact of failure

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Purpose of Database System

In the early days, database applicationswere built on top of file systems

Drawbacks of using file systems to storedata: Data redundancy and inconsistency

Multiple file formats, duplication of information in different files

Difficulty in accessing data

Need to write a new program to carry out each new task

Data isolation multiple files and formats

Integrity problems

Integrity constraints (e.g. account balance > 0) become part ofprogram code

Hard to add new constraints or change existing ones

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Contd..

The range of database can be divided into fivecategories:

Personal Database-support one user-improve

personal productivity.Workgroup-a relatively small team of people

who collaborate on the same project orapplication.

Departmental database-functional unit within anorganization, larger than workgroup and isresponsible for a more diverse range offunctions.

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Contd..

Enterprise database- the entire organizationor enterprise or many different departmentsdatabase. Such database are intended tosupport organization wide operations anddecision making.

Internet database- database of huge

information available in internet.

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Level of abstraction3rd Lecture-14.09.10)

A database abstraction layer is anapplication programming interface whichunifies the communication between a

computer application and databases. Database abstraction layers reduce the

amount of work by providing a consistent

API to the developer and hide the databasespecifications behind this interface as much aspossible

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Levels ofabstraction

The database description consists ofa schema

at eachofthese three levels ofabstraction:

Conceptual level

physical level

View level

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Levels ofAbstraction

Logical level: describes data stored indatabase, and the relationships among thedata.

The conceptual or logical level describesthe stored data in terms of the data model ofthe DBMS.

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Contd

In a relational DBMS, the conceptual schemadescribes all relations that are stored in thedatabase.

In university database, these relations containinformation about entities, such as studentsand faculty, and about relationships, such as

students enrollment in courses.

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Contd..

Students(sid: string, name: string, login: string,

age: integer, gpa: real)

Faculty(d: string, fname: string, sal: real)

Courses(cid: string, cname: string, credits: integer)

Rooms(rno: integer, address: string, capacity:integer)

Enrolled(sid: string, cid: string, grade: string)

Teaches(d: string, cid: string)

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Contd..

Physical level describes how a record isstored. Essentially, the physical levelsummarizes how the relations described in theconceptual schema are actually stored onsecondary storage devices such as disks andtapes.

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Contd..

View level-defines a view or views of thedatabase for particular users.

Any given database has exactly oneconceptual schema and one physical schemabecause it has just one set of stored relations,but it may have several external schemas, each

tailored to a particular group of users.

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View ofData

An architecture for a database system

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Data Model

A data model is an abstract model thatdescribes how data are represented andaccessed.

Data models formally define data elementsand relationships among data elements for adomain of interest.

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Contd..

Data models are a collection of tools fordescribing data, data relationships, datasementics and data constraints.

Data models are

Entity-relationship model

Relational model

Network model

Object model

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Contd..

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Entity

An entity is a concept or concrete thing in thereal world that we want to model in a database.

Atomic real world item.

Anything that can be distinguished from anyother thing.

Eg book, customer, payment mode etc.

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Entity set

Collection of similar entities.

Same set of attributes

Has a keyEach attribute has a domain.

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Weak entities

Existance depends on some other entity.

a Weak Entity is an entity that cannot be

uniquely identified by its attributes alone;therefore, it must use a foreign key inconjunction with its attributes to create aprimary key.

claims, orders and invoices,

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Attributes(4th Lecture-16.09.10)

A property of an entity type.

An entity is represented by a set of attributes,

that is descriptive properties possessed by allmembers of an entity set.

Example:

customer = (customer-id, customer-name,customer-street, customer-city)

loan = (loan-number, amount)

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Contd..

Domain the set of permitted values for eachattribute.

Types of attributes

Simple attribute

Composite attribute

Single valued

Multivalve

Derived

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Relationship

Represents an association between two ormore entities.

It is a link between two entities, and it tellssomething about which relationships existsbetween our entities.

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Degree of Relationship

It is the number of entities associated withthe relationship.

The n-ary relationship is the general form fordegree n.

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connectivity

Describes the mapping of associated entityinstances in the relationship.

The values of connectivity are one ormany

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Cardinality

It expresses the specific number of entityoccurrences associated with one occurrence ofthe related entity.

The basic types of connctivity for relationsare:

One-to-one

One-to-many

Many-to-many

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Contd..

One toone One to many


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Contd..

Many toone Many to many


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Keys(5th Lecture, 20/9/10)

Minimum set of attributes whose valuesuniquely identify an entity in the set.

It identifies a set of attributes thatdistinguish entities from each other.

Super key

Candidate key

Primary key

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E-RModel

Originally proposed by Peter in 1976.

It is a conceptual data model that views the

real world as entities and relationships.

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E-RDiagrams

Rectangles represent entity sets.

Diamonds representrelationship sets.

Lines link attributes to entity sets and entity sets torelationship sets.

Ellipses represent attributes

Double ellipses represent multivalued attributes.

Dashed ellipses denote derived attributes.

Underline indicates primary key attributes (will study later)


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E-RDiagram WithComposite, Multivalued, andDerived

Attributes


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Relationship Sets with Attributes


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Cardinality Constraints

We express cardinality constraints by drawing

either a directed line (p), signifying one, oran undirected line (), signifying many,between the relationship set and the entity set.

E.g.: One-to-one relationship: A customer is associated with at most one loan via the relationship borrower

A loan is associated with at most one customer via borrower


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Many-To-One Relationships

In a many-to-one relationship a loan isassociated with several (including 0) customersvia borrower, a customer is associated with atmost one loan via borrower

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