Systems Analysis and Design

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Systems Analysis and Design

• Lecture 5
• BUS 391
• Professor Barry Floyd

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AGENDA

• Building Information Systems ...
• Systems Development Life Cycle
• Alternative Approaches to System Development

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The Systems Development Life Cycle

• Plan
• Analysis
• Design
• Develop
• Test
• Implement
• Maintain

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Systems Analysis

• A process of understanding a users needs and
  from those needs deriving the functional and
  performance requirements of the a system.
• Functional requirements What functions (tasks)
  the system must be able to do.
• Performance requirements How well does the
  system perform those tasks.

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Systems Design

• A process of constructing a system to perform the
  functional requirements needed by the user.

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Computer based systems for business are difficult
to build successfully because ...

• Users dont understand problem, but theyll know
  solution when they see it.
• Analyst doesnt understand problem domain
• Problem domains can be very complex
• Requirements change
• Difficult to manage the development process
• Software is so flexible--almost too flexible!

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Participants in a Systems Development Project
MANAGEMENT
USER GROUP
ANALYSTS / PROGRAMMERS
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Plan

• Define the system to be developed
• CSF
• Set the project scope
• Key aspect of SDLC, difficult to do scope creep
  
• Develop the project plan including tasks,
  resources, and timeframes

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Analysis - Definition

• Getting to know the application.
• Computer technology appropriate? How?
• Defining processing, requirements, constraints,
  costs, and benefits.
• Developing functional specifications and
  prototypes.
• Reviewing specifications and prototypes.

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Output Requirements
Who gets the output? When? What type of
output? What are the contents? .....
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INPUT REQUIREMENTS
What input? How many transactions? Peaks /
Valleys? What form? Time to enter? ....
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FILE AND STORAGEREQUIREMENTS
How much? Programs / Data? Future
requirements? How quickly do you need it?
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PROCESSING REQUIREMENTS
Payroll Data
Checks
Print Paychecks
DEFINE ACTIVITIES TO TRANSFORM INPUTS INTO OUTPUTS
Distribute Paychecks
Checks
Employees
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Dataflow Diagrams

• DATA FLOW
• DATA STORAGE
• EXTERNAL SOURCES / SINKS
• DATA PROCESSES

Checks
Employees
Print Paychecks
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Design

• Putting together the parts (software, hardware,
  people, procedures, data) to provide the
  functionality with the right operating
  characteristics within budget and on schedule.
• What gets designed?
• - input forms - output reports
• - screens - data files
• - procedures - data security
• - data controls - contingency plans
• ...

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Develop

• Build Technical architecture
• Build the database and programs
• Programmer teams
• Structured Walkthroughs

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Test

• Write the test conditions
• Functions performed correctly
• Usability / acceptance
• Stress (e.g., enough ummph to handle all users)
• Perform the testing of the system

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Implement

• Install system into the organization
• User Documentation
• Training

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Maintain

• Build a help desk to support system users
• Provide an environment to support system changes

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Alternative Development Techniques

• Prototyping
• SDLC vs. Prototyping
• Application Packages
• End User Computing

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Prototyping

• Goal is to quickly develop a working model of the
  system, use the model to gain knowledge about
  final system.
• Must have tools which allow the analyst to
  quickly develop and test prototypes.
• Very important for developing look and feel to a
  system.

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SDLC vs. Prototype
Analyst Doesnt Know
PROTOTYPING
Analyst Knows
SDLC
User Knows
User Doesnt Know
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Application Packages
- - - -

• Speed of acquisition
• User groups
• Low cost
• Possible to customize
• Develop skills
• Assured what it can do
• Low risk

• May not meet needs exactly
• No competitive advantage
• Improve at rate of developer and in direction
  developer wants
• Dont develop inhouse expertise

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End-User ComputingSelf-sourcing

• Provide systems and skills for users to roll
  their own

• Skilled workers in control!
• Decentralization
• Rapid development
• No user - developer communications problems

• Ad hoc development
• no standards
• no doc
• Application may disappear when user moves

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Why systems fail?

• Unclear or missing requirements
• Skipping SDLC phases
• Failure to manage project scope
• Failure to manage project plan
• Changing technology

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Summary

• The Systems Development Life Cycle is an
  important approach to developing systems
• There is a place for everyone in the organization
  to participate in this activity, the more you
  know about the process and outputs, the better
  the system will be.