Quality assurance using software engineering

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Quality assurance using software engineering

• delivered by John Stockwell

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Objectives

• At the end of this lecture you will be able to
• Describe the quality advantages of adopting a
  top-down modular approach to systems design
• Explain how quality is enhanced by using the
  correct techniques for documenting
• Discuss the importance of testing, maintaining
  and auditing software

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QA using software engineering

• Design systems with a top-down modular approach
• Document software with appropriate tools
• Test, maintain and audit software

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TQM total quality management

• an evolutionary process towards perfection
• Continuous improvement
• Strategic planning and leadership
• Customer focus
• Empowerment
• Teamwork

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Responsibility for TQM

• Must have management support
• Analysts must consider quality right from the
  inception of a project and not merely as an
  afterthought to solve problems at the end
• Organisational support must exist
• On the job time for IS quality circles
• Guidelines must be developed for quality standards

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Structured walkthrough

• Use peer reviewers to monitor systems
  programming and overall development
• Allows analyst and programmer to make revisions
• Co-ordinator, originator of model/code
  (analyst/programmer) and analyst/programmer peer
  take part
• Implemented whenever a subsystem has been
  completed

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Quality and System Design Approach

• Bottom-up
• Identifies processes to be computerized at the
  lowest level of the organization
• Makes it difficult to interface with subsystems
  interface problems
• Duplication of effort in purchasing software and
  entering data
• Overall organizational objectives not considered

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Quality and System Design Approach

• Top-down
• Look at the large picture and explode it into
  smaller subsystems
• Overall organizational objectives considered
• Emphasis on interrelationships between subsystems
• Enables separate analysis teams to work in
  parallel
• Focuses on what the system is supposed to do as
  opposed to individual sub systems
• Must manage reintegration of subsystems
• Fits well with TQM

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Quality and System Design Approach

• Modular
• Used with top down approach
• Breaks program into manageable chunks
• Emphasises interfaces between modules
• Modules are self contained and easy to test,
  debug, understand and maintain
• Uses structure charts

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Structure charts

• Structure charts
• Show the relationships among program modules
• Chart symbols represent
• Modules
• Data couples
• Control couples
• Conditions
• Loops

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Example structure chart
Main_program
Income status
status
Income Status tax
income
tax
Entered_filing_status
Entered_gross_income
Output_results
Computed_tax
Print_status_menu
status
Print_status
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Software engineering and documentation

• Process and software documentation is necessary
  to allow for
• New users
• New programmers maintaining system
• Techniques include
• Nassi-Shneiderman charts
• Pseudocode
• Procedure manuals

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Nassi-Shneiderman charts
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Pseudocode example

• public boolean moveRobot (Robot aRobot)    
  //IF there is no obstacle in front THEN        
  // Move the robot         // Add the move
  command to the command history         // RETURN
  true     //ELSE         // RETURN false without
  moving the robot     //END IF

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Code Generation and Design Engineering

• Use of software to create all or part of a
  computer programme
• CASE tool forward engineering
• See demonstration of Together CASE tool

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Testing Maintenance and Auditing

• Testing subsystems then whole system
• Testing with test data
• Desk check programs then create test data
• Link testing with data
• Full systems testing with data
• Full systems testing with live data
• Maintenance Practices
• More to improve software than to fix it
• Auditing
• An expert examines information to gauge its
  reliability

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Summary

• The systems analyst uses three broad approaches
• designs systems and software with a top-down
  modular approach
• documents software systematically using
  appropriate tools
• Organises testing, maintaining and auditing of
  the system and software

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References

• Dean, Jr., J. W., and Evans J.R., Total Quality,
  West Publishing Company, 1994
• Kendall K., Kendall J., Systems Analysis and
  Design, Prentice Hall, 2002 (fifth edition)