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1. Information System Development
INFROMATION SYSTEM PART 2 BY SUJITH
R

2. Information System Development
Feasibility
Analysis
Design
Implementation
Test
Maintain
SDLC - Classic Waterfall model

3. Information System Development
Prototype
A prototype is a working system to explore
implementation or processing alternatives and
evaluate results
•SDLC takes too long
•The right system is rarely developed the first time

4. Information System Development
Prototype are used when ……
• No system of the proposed type has been constructed so far
• Essential features of the system are partially known and they are not
identifiable even after careful analysis of the existing system
• Using the system will add to requirement lists
• Alternate systems will evolve through experience
• User participation very effective

5. Information System Development
Steps towards prototyping
• Identify the user requirements
• Develop a working prototype.
• Allow the user to use the prototype and collect feedbacks
• Modify the existing prototype incorporating the feedbacks
• Repeat for the next version …..

6. Information System Development
RAD (RAPID APPLICATION DEVELOPMENT)
• Planning
• Analysis
• Design
• Build
• Test
• Deploy
Compressed

7. Information System Development
RAD
Advantages
• Increased speed of development
• Increased quality
Disadvantages
• Reduced scalability
• Reduced features

8. Information System Development
Requirement Analysis – requirements definitions and gathering
• Requirement elicitation (gathering customer needs)
• Requirement analysis (understanding a problem and requirements of
a workable solution)
• Requirement specification (description of what the system will do)
should be complete, comprehensive, testable, consistent,
unambigous,writable, modifiable and implementable.
• Requirements management (process that helps the team to identify,
control and track changes)

9. Information System Development
Logical Design
• Define boundaries
• Inputs
• Outputs
• Data stores
• Procedures
DESIGN OF A SYSTEM
Physical Design
• Input / Output Media
• Database design
• Decide software platforms
• Implementation plan
• Testing procedures

10. Information System Development
• Flowcharts
• Data flow diagrams (DFD’s)
• Data dictionary
• Structured English
• Decision table
• Decision tree
Tools for System Design

11. Information System Development
Flowcharts are pictorial representation of program logic.
• Shows step by step solution to a problem
• Easy to understand graphical representation
• Provides clear documentation
• Is complex for larger problems
Flowcharts

12. Information System Development
Symbols in Flowcharts
Y N
Start / Stop
Input / output
Decision Box
Process Box
Flow of Control
Connectors

13. Information System Development
Flowcharts
Start
Input A,B
Is
A > B
Print BPrint A
Stop
Y N

14. Information System Development
DFD is a structured diagrammatic technique for
showing the functions performed by a system and
the data flowing into, out of and within it.
Data Flow Diagrams (DFD’s)
DFD’s Show ……
• The processes within the system
• The datastores (files) supporting its operation
• The information flows within it
• The system boundary
• Interactions with external entities

15. Information System Development
Customer
Sales1
Order
Rejected
Order
Dispatch
Note
2 Warehouse
Dispatch
Goods
3 Accounts
Maintain Credit
Ratings
D1 Credit
Rating
Check Credit
Rating
A Complete DFD

16. Information System Development
Customer
Sales
Check Credit
Rating
D1 Credit
Rating
A Data Flow
An External Entity
A Process
A Data Store
3
DFD Symbols

17. Information System Development
Sales
Check Credit
Rating
3
Unique Number Where it’s done
What’s done
Output Data
Input
Data
The Process Symbol

18. Information System Development
Customer
D1 Credit
Rating
A Duplicated External Entity
Duplicated Data Store
Customer
Repeated Symbols – to avoid crossing lines, data
stores and external entities can be repeated:
D – Computerised Data file
M – Manual file

19. Information System Development
A wines and spirits wholesaler stocks a range of approximately 400
different lines and delivers by van on regular weekly runs to customers
who are mainly off-licenses and clubs. The majority of orders are received
by telephone and any one customer may place several orders during the
week which must be accumulated and delivered in one consignment.
When a customer telephones he expects to be advised on the availability
of an item requested and, if not in stock, the alternatives that are
available. At present, sales order forms are filled in by the telephone
salesmen and sent to the warehouse where they are used for the
despatch of the items. Hand-written despatch notes are used as the basis
of the invoices which are typed and sent by post sometime later.
Prepare a dataflow diagram (DFD) which represents the above system.

20. Information System Development
customer
customer
Stock file
Accumulate orders
Advise availability
Complete forms
1 Sales
Sales Order Forms
2
Produce despatch
notes
Produce Invoices
InvoiceDespatch note +
goods
Warehouse
The DFD
Order Advice
M1

21. Information System Development
This is a catalog or a repository of data about data
(Metadata). A list of all the elements composing the
data flowing through the system will be found here.
The major elements are data flows, data stores and
processes.
Data Dictionary

22. Information System Development
Is a modified form of the English language used to
specify the logic of information system processes.
Although there are no standards, Structured English
normally relies on action verbs and noun phrases
and contains no adjectives or adverbs
Structured English

23. Information System Development
Are used to lay out all possible situations which a
business decision may encounter and to specify the
action to be taken in each of the situation in a
tabular form.
Decision Table
Printer troubleshooter
Rules
Conditions
Printer does not print Y Y Y Y N N N N
A red light is flashing Y Y N N Y Y N N
Printer is unrecognised Y N Y N Y N Y N
Actions
Check the power cable X
Check the printer-computer cable X X
Ensure printer software is installed X X X X
Check/replace ink X X X X
Check for paper jam X X

24. Information System Development
A decision tree is a
diagram that
represents
conditions and
actions sequentially
and thus shows
which conditions to
consider first, which
second and so on.
Decision Tree

25. Information System Development
• How to execute the package
• How to enter data
• Processing details
• Generating reports
Implementation and Maintenance

26. Information System Development
• Parallel run
• Pilot run / Phased run
Implementation and Maintenance
Overall Evaluation
• Operational
• Organisational
• User Manager assesment
• Development performance

27. Information System Development
Make or Buy Decision for Information systems
Packaged solutions Custom-built
solutions
Hybrid solutions
What it means Complete solution
provided by a vendor
Custom build /
Tailor made from
scratch
Partially packaged /
partially custom built
Potential
benefits
• Cheaper
• Quality
• Future migrations
• Better fit
• More control
• Fine tuned
• Best of solutions
• Customization
Potential risks • Stability of Vendor
• Process changes
• Experience
• Immature skills
• Time factor
• Future changes
• Skill set issues
• Integration
• Vendor experience
Costs to
consider
• License
• Support
• Training
• Quality assurance
• Infrastructure
• Development
• Technology
• Quality assurance
• License
• Support
• Training
• Development