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Information Systems

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Information System (CS507)
LESSON 26
Symbols
Entity Relationship Diagram as a technical tool also has predefined set of symbols. The purpose behind all
this is to have standardization in the use of technique in varied situations. Some major symbols
commonly used are as under.
Entity (a real world object)
Attributes (of an entity)
Relationship (between two entities)
Lines link attributes to entity sets,
entity sets to relationship sets (also
represent roles)
Double ellipses represents multi-
valued attributes
Primary key attributes are
EmpID
underlined.
Dashed ellipses represent derived
attribute.
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ERD Example
Name
Dept. ID
Dept. Name
Emp. ID
Phone
Hire Date
Works In
Employees
Departments
No. of employees
College Degree
The diagram shows a primary relationship is between two entities, employee and the department. The
relationship is of an employee working in a department. The figure also shows information available for
each of these entities.
Object Oriented Analysis and Design (OOAD)
The concept of object oriented analysis and design focuses on problems in terms of classes and objects.
This concept combines aspects of both entity relationship diagram and data flow diagrams. The object
oriented analysis and design tool has been devised to support the object oriented languages, for example
C++ and Java. The roots of the concept of object orientation evolved in late 60's with the emergence of
first language "SIMULA 67" as the first object oriented language. Object oriented methodologies do not
replace traditional approaches (such as data flow, process flow, and state transition diagrams); they are
important new additions to the toolkit.
26.1 Why need Object-Orientation?
There are certain positive points which are becoming stronger reasons for the increased use of this
technique.
Object orientation helps in increasing abstraction and event-driven programming
The widespread use of Graphical User Interface (GUI) encourages use of object orientation.
Software can be developed on modular basis
1. Easier to maintain
2. Easier to upgrade
3. Easier to test
4. Easier to develop incrementally
Reusable Software ­ The software developed using object oriented approach can be easily reused
due to independence/uniqueness of the objects i.e. an independent accounting module built in
object oriented environment can be made a part of a complete ERP solution without developing it
again from scratch for ERP.
26.2 Object Oriented Analysis
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The concept of analysis has been defined from different perspectives in different approaches to system
development.
"The development activity consisting of the discovery, modeling, specification and evaluation of
requirements,"
Donald Firesmith (Dictionary of Object Technology, 1995),
In OOAD analysis has been defined in a different manner
"The discovery, analysis and specification of requirements in terms of objects with identity that encapsulate
properties and operations, message passing, classes, inheritance, polymorphism and dynamic binding."
Object oriented Design
The concept of design has been defined from different perspectives in different approaches to system
development.
"Systems design is the process or art of defining the hardware and software architecture, components,
modules, interfaces, and data for a computer system to satisfy specified requirements."
In OOAD analysis has been defined in a different manner. According to Firesmith
"The design of an application in terms of objects, classes, clusters, frameworks and their interactions is
called OOAD Analysis."
Basic Concepts
Following are the basic concepts related to this technique.
An object is defined as
"an abstraction of something in a problem domain, reflecting the capabilities of the system to keep
information about it, interact with it, or both."
Coad and Yourdon (1990)
An object is any abstraction that models a single concept.
Another Definition of object
"A concept, abstraction, or thing with crisp boundaries and meaning of the problem at hand. Objects serve
two purposes. They promote understanding of the real world and provide a practical basis for computer
implementation."
Rumbaugh et al. (1991)
Components of object
According to Booch, there are three components of object. Objects have state, behavior and identity.
Identity: Who is it?
Each object has unique identity.
Behavior: What can it do?
What an object can do, how it can respond to events and stimuli.
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State: What does it know?
The condition of an object at any moment, affecting how it can behave
Real-world objects share two characteristics: They all have state and behavior.
For example,
 Dogs have state (name, color, breed, hungry) and behavior (barking, fetching, wagging tail).
 Bicycles have state (current gear, current pedal cadence, two wheels, number of gears) and behavior
(braking, accelerating, slowing down, changing gears).
Objects ­
Object
Identity
Behaviour
States
`Ahmad'
Speak, walk,
Studying, resting,
A
qualified, working.
read, eat, talk,
person.
think.
white denim
Shrink, stain,
Pressed, dirty,
A shirt.
shirt
rip.
worn.
Invoiced,
Company:
Transaction no.
A sale.
Generate
060501 & date
June 12, 2006
mode of payment:
income.
cash/credit
Customer: Earn
Bonus
points/Rebates
Adds tang to the Unsold, opened,
A bottle  Tomato, garlic,
chilli ketchup
meal
empty, spilt in
of
transit
ketchup.
Examples
Software objects are modeled after real-world objects in that they too have state and behavior. We might
want to represent real-world dogs as software objects in an animation program or a real-world bicycle as
software object in the program that controls an electronic exercise bike.
Classes
A class is defined as
"The purpose of a class is to specify a classification of objects and to specify the features that characterize
the structure and behavior of those objects."
A class is any uniquely identified abstraction, that is, model of a set of logically related objects that share the
same or similar characteristics. The purpose of a class is to specify a classification of objects and to specify
the features that characterize the structure and behavior of those objects.
An object is an instance of some class. All objects are instances of some class. Instance also carries
connotations of the class to which the object belongs.
For example, computers are the domain/Class which can be divided into following sub-classes:
 Laptop computer
 Desktop computer
 Palmtop
In the sub-sub-class of laptops, we may identify various laptop models or brands which may then have a
further division on a model-wise basis.
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Table of Contents:
  1. Need for information, Sources of Information: Primary, Secondary, Tertiary Sources
  2. Data vs. Information, Information Quality Checklist
  3. Size of the Organization and Information Requirements
  4. Hierarchical organization, Organizational Structure, Culture of the Organization
  5. Elements of Environment: Legal, Economic, Social, Technological, Corporate social responsibility, Ethics
  6. Manual Vs Computerised Information Systems, Emerging Digital Firms
  7. Open-Loop System, Closed Loop System, Open Systems, Closed Systems, Level of Planning
  8. Components of a system, Types of Systems, Attributes of an IS/CBIS
  9. Infrastructure: Transaction Processing System, Management Information System
  10. Support Systems: Office Automation Systems, Decision Support Systems, Types of DSS
  11. Data Mart: Online Analytical Processing (OLAP), Types of Models Used in DSS
  12. Organizational Information Systems, Marketing Information Systems, Key CRM Tasks
  13. Manufacturing Information System, Inventory Sub System, Production Sub System, Quality Sub system
  14. Accounting & Financial Information Systems, Human Resource Information Systems
  15. Decision Making: Types of Problems, Type of Decisions
  16. Phases of decision-making: Intelligence Phase, Design Phase, Choice Phase, Implementation Phase
  17. Planning for System Development: Models Used for and Types of System Development Life-Cycle
  18. Project lifecycle vs. SDLC, Costs of Proposed System, Classic lifecycle Model
  19. Entity Relationship Diagram (ERD), Design of the information flow, data base, User Interface
  20. Incremental Model: Evaluation, Incremental vs. Iterative
  21. Spiral Model: Determine Objectives, Alternatives and Constraints, Prototyping
  22. System Analysis: Systems Analyst, System Design, Designing user interface
  23. System Analysis & Design Methods, Structured Analysis and Design, Flow Chart
  24. Symbols used for flow charts: Good Practices, Data Flow Diagram
  25. Rules for DFDs: Entity Relationship Diagram
  26. Symbols: Object-Orientation, Object Oriented Analysis
  27. Object Oriented Analysis and Design: Object, Classes, Inheritance, Encapsulation, Polymorphism
  28. Critical Success Factors (CSF): CSF vs. Key Performance Indicator, Centralized vs. Distributed Processing
  29. Security of Information System: Security Issues, Objective, Scope, Policy, Program
  30. Threat Identification: Types of Threats, Control Analysis, Impact analysis, Occurrence of threat
  31. Control Adjustment: cost effective Security, Roles & Responsibility, Report Preparation
  32. Physical vs. Logical access, Viruses, Sources of Transmissions, Technical controls
  33. Antivirus software: Scanners, Active monitors, Behavior blockers, Logical intrusion, Best Password practices, Firewall
  34. Types of Controls: Access Controls, Cryptography, Biometrics
  35. Audit trails and logs: Audit trails and types of errors, IS audit, Parameters of IS audit
  36. Risk Management: Phases, focal Point, System Characterization, Vulnerability Assessment
  37. Control Analysis: Likelihood Determination, Impact Analysis, Risk Determination, Results Documentation
  38. Risk Management: Business Continuity Planning, Components, Phases of BCP, Business Impact Analysis (BIA)
  39. Web Security: Passive attacks, Active Attacks, Methods to avoid internet attacks
  40. Internet Security Controls, Firewall Security SystemsIntrusion Detection Systems, Components of IDS, Digital Certificates
  41. Commerce vs. E-Business, Business to Consumer (B2C), Electronic Data Interchange (EDI), E-Government
  42. Supply Chain Management: Integrating systems, Methods, Using SCM Software
  43. Using ERP Software, Evolution of ERP, Business Objectives and IT
  44. ERP & E-commerce, ERP & CRM, ERP Ownership and sponsor ship
  45. Ethics in IS: Threats to Privacy, Electronic Surveillance, Data Profiling, TRIPS, Workplace Monitoring