Information System

1
Information System

• IS a set of related components working together
  in some environment to perform functions that
  achieve some objective.

2
Organizational policies
Process
Input
Output
Standard operating procedures
Customers
Government Regulations
Competitors
Shippers
3

• IS Functions
• Input, Processing, Output, Storage, Controls
• IS Components
• People, Procedures, Data, Software, Hardware
• Alternative Object-oriented view of a system

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Object-Oriented Systems

• Object
• Attributes - characterize an object
• Methods - the objects behavior

DOG
DOG OWNER
VET
Name Sex Breed
Name Address
Name Speciality
Throw MakePayment
GiveTreatment BillCustomer
fetch
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• Object class
• set of objects with common attributes and
  functions
• Object Instance
• has specific values for attributes
• can perform all methods of the class

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O-O systems Inheritance
People
Vet
Dog Owner
.
.
Cathy
Fred
People
Vet
DogOwner
Fred
Cathy
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O-O systems Inheritance
People
Dog Owner
Vet
.
.
Fred
Cathy
People
Vet
DogOwner
Multiple inheritance
Cathy
Fred
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Systems Development the process

• System lifecycle
• development phase
• production phase
• Systems approach
• divide and conquer

conversion
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Systems Development the process

• System Analysis
• study business problem domain, existing system
• identify requirements
• specify characteristics of new system
• System decomposition
• by functions performed
• in terms of objects

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Systems Development the process

• System Design
• evaluate alternative solutions, design a
  chosen solution
• design document basis for implementation

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Two system development approaches

• Functional Decomposition
• identify major activities, break up into
  composite steps (structured analysis and
  design)
• focus on verbs (what a system does)
• Objects that comprise the system and how they act
  and relate
• object structure and behavior analysis
• focus on nouns (objects performing functions)

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SDLC

• System development methodology
• activities to solve a problem
• A methodology uses certain techniques
• (used to model a system)
• Model
• representation of real world
• used in analyzing and communicating what we
  understand
• DATA MODELS, PROCESS MODELS, OBJECT MODELS, etc.

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System development catalysts

• User demand
• problems in current system, need for
  enhancements, improved efficiency
• Technology push
• new technology as catalysts
• Strategic pull
• system to support new business strategies/
  products to stay competitive

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Projects of varying complexity

• Upto 1000 lines
• trivial, single person, few days/week
• 1000-10,000 lines
• simple, 3/4 progr/analyst, 6-12 months
• often formal analysis and design not used, but
  could be - leads to more maintainable system
• 10,000-100,000 lines
• difficult, 6-12 people, 2-3 years
• formal analysis and design essential
• requirements/users change over time
• 100,000 - 1 million lines
• complex. 50-100 people, 3-5 years
• diverse community of users
• 1-10 million lines
• nearly impossible
• gt 10 million
• absurd??

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Why do IS projects fail?

• Did not support business strategy objectives
• poor planning, project management
• failure to understand user requirements
• user involvement in system development
• inadequate cost vs. benefit analysis
• escalating costs, intangible benefits
• myriad of design defects/ errors
• installation of incompatible or inadequate
  technology
• no adequate controls implemented
• unstructured, un-maintainable software

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Successful systems development

• Informal, sloppy art structured, engineered
  and managed approach (SDLC)
• stress user involvement in system development
• system planning and project management
• evaluate alternate designs before committing
• clean, complete and up-to-date documentation
• design for growth and change

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Bugs!

• software errors cost U.S. users 59.5 billion
  each year. (National Institute of Standards and
  Technology (NIST)
• just the cost of routine work-arounds and
  corrections by users, along with the added cost
  of buggy software that had to be fixed late in
  the development process. The real cost of bugs is
  much higher.
• 22.2 billion of that 59.5 billion, or 37,
  could be saved through "feasible improvements" in
  software testing.
• We indulge ourselves with the idea that all
  software has bugs, so trying harder to get rid of
  them is pointless perfectionism. Intellectually
  we should know better !

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Software the product

• Software a strategic business issue, not just a
  low-level support activity
• Can software be manufactured like physical
  products? (software factories)
• Costs are concentrated on engineering (design)
  and support
• mythical man-month
• Adding people to a project that is late
  will only worsen the situation. Why?
• Efficiency through re-use

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Failure Curves
Wear out
Changes
Infant mortality
Failure Rate
Actual
Ideal
Time
Hardware
Software
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The Systems Analyst

• Roles
• as a CONSULTANT (external)
• provide a fresh perspective
• disadvantage organizational culture may not be
  known
• as a SUPPORTING EXPERT
• as a CATALYST FOR CHANGE
• interact with management
• excellent with people and machines
• analyze need for change, design change with
  consensus, implement change

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The Systems Analyst

• Qualities
• problem solver
• good analysis skills
• tools and techniques for analysis
• communicator
• computer skills
• knowledge of business processes
• self-disciplined and self-motivated

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IS Building Blocks

• People
• Data
• Activities
• Networks
• Technology

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IS Building Blocks PEOPLE

• System Owners
• sponsors, advocates
• budgeting, time and money
• responsible for ultimate acceptance
• System users
• need for communication with users during AD
• different user groups with diff. info. Needs
• System designers
• translate business/user requirements and
  constraints into technical solutions
• System builders
• implement system based on design specifications

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IS building blocks DATA

• System owners view
• info. on business resources
• avoid details, focus on business entities of
  interest
• System users view
• data experts, how data is used
• identify data requirements, independent of
  implementation (entities, attributes, and rules)
• System designers view
• files and databases
• System builders view
• implement files, DBs, etc.

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IS building blocks ACTIVITIES

• System owners view
• big picture
• System users view
• distinct processes and their detail
• SA elicits processing requirements from users
• NOTEusers often biased by current system
• System designers view
• technology constraints
• specifications DFDs, structure charts, E/R, etc
• System builders view
• application programs

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IS building blocks NETWORKS

• (distributed people, processes, data)
• System owners view
• geographic scope, locations
• System users view
• details, data flow between locations, local data
  storage
• System designers view
• system architecture, sharing/duplication of data,
  communication between machines
• System builders view
• network control programs