Download - Infromation System1
-
8/8/2019 Infromation System1
1/47
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
-
8/8/2019 Infromation System1
2/47
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)
2
-
8/8/2019 Infromation System1
3/47
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
3
-
8/8/2019 Infromation System1
4/47
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
-
8/8/2019 Infromation System1
5/47
Contd..
Data Information Knowledge Action
5
-
8/8/2019 Infromation System1
6/47
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
6
-
8/8/2019 Infromation System1
7/47
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)
7
-
8/8/2019 Infromation System1
8/47
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.
8
-
8/8/2019 Infromation System1
9/47
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
9
-
8/8/2019 Infromation System1
10/47
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.
10
-
8/8/2019 Infromation System1
11/47
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.
11
-
8/8/2019 Infromation System1
12/47
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
12
-
8/8/2019 Infromation System1
13/47
Disadvantage
Complexity
Size
Cost of DBMS
Additional hardware cost
Performance
Higher impact of failure
13
-
8/8/2019 Infromation System1
14/47
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
14
-
8/8/2019 Infromation System1
15/47
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.
15
-
8/8/2019 Infromation System1
16/47
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.
16
-
8/8/2019 Infromation System1
17/47
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
17
-
8/8/2019 Infromation System1
18/47
Levels ofabstraction
The database description consists ofa schema
at eachofthese three levels ofabstraction:
Conceptual level
physical level
View level
18
-
8/8/2019 Infromation System1
19/47
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.
19
-
8/8/2019 Infromation System1
20/47
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.
20
-
8/8/2019 Infromation System1
21/47
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)
21
-
8/8/2019 Infromation System1
22/47
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.
22
-
8/8/2019 Infromation System1
23/47
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.
23
-
8/8/2019 Infromation System1
24/47
View ofData
An architecture for a database system
24
-
8/8/2019 Infromation System1
25/47
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.
25
-
8/8/2019 Infromation System1
26/47
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
26
-
8/8/2019 Infromation System1
27/47
Contd..
27
-
8/8/2019 Infromation System1
28/47
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.
28
-
8/8/2019 Infromation System1
29/47
Entity set
Collection of similar entities.
Same set of attributes
Has a keyEach attribute has a domain.
29
-
8/8/2019 Infromation System1
30/47
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,
30
-
8/8/2019 Infromation System1
31/47
-
8/8/2019 Infromation System1
32/47
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)
32
-
8/8/2019 Infromation System1
33/47
Contd..
Domain the set of permitted values for eachattribute.
Types of attributes
Simple attribute
Composite attribute
Single valued
Multivalve
Derived
33
-
8/8/2019 Infromation System1
34/47
Relationship
Represents an association between two ormore entities.
It is a link between two entities, and it tellssomething about which relationships existsbetween our entities.
34
-
8/8/2019 Infromation System1
35/47
Degree of Relationship
It is the number of entities associated withthe relationship.
The n-ary relationship is the general form fordegree n.
35
-
8/8/2019 Infromation System1
36/47
connectivity
Describes the mapping of associated entityinstances in the relationship.
The values of connectivity are one ormany
36
-
8/8/2019 Infromation System1
37/47
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
37
-
8/8/2019 Infromation System1
38/47
Contd..
One toone One to many
-
8/8/2019 Infromation System1
39/47
Contd..
Many toone Many to many
-
8/8/2019 Infromation System1
40/47
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
40
-
8/8/2019 Infromation System1
41/47
E-RModel
Originally proposed by Peter in 1976.
It is a conceptual data model that views the
real world as entities and relationships.
41
-
8/8/2019 Infromation System1
42/47
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)
-
8/8/2019 Infromation System1
43/47
E-RDiagram WithComposite, Multivalued, andDerived
Attributes
-
8/8/2019 Infromation System1
44/47
Relationship Sets with Attributes
-
8/8/2019 Infromation System1
45/47
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
-
8/8/2019 Infromation System1
46/47
-
8/8/2019 Infromation System1
47/47
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