Software Quality Management

Software Quality Management

1. What is Software Quality?

   • "Conformance to requirements" [Crosby]
   • PRODUCT QUALITY
     • Provide functions when the user needs them.
       • Ease of installation
       • Operational Efficiency
       • Convenience
     • Must work.
   • PROCESS QUALITY
     • The user is the Software Engineer
     • PSP that meets you need to efficiently produce quality products.

2. The Economics of Software Quality

   • THE COST OF FINDIND AND FIXING DEFECTS
     • Determining that there's a problem
     • Isolating the source of the problem
     • Determining what's wrong with the product
     • Fixing requeriments as needed
     • Fixing the design
     • Fixing the implementation
     • Inspecting the fix to ensure it's correct
     • Testing the fix
     • Changing the document as needed to reflect the fix
   • THE COST OF QUALITY
     • A way to "quantify the size of the quality problem in language that'll have impact on upper management." [Juran]
     • Failure costs
     • Appraisal costs
     • Prevention costs

3. Developing a Quality Strategy

   • Measure your process
   • Determine the most effective quality methods
   • Periodically reevaluate your strategy

4. Process Benchmarking

   • Measure the ability of the process to produce high-quality products.
   • Provide a clear ordering of process performance from best to worst
   • Indicate teh ability of the process to withstand perturbations or disruptions
   • Provide required data that is objectively measurable
   • Provide data in a timely manner
   • BENCHMARKING CONSIDERATIONS
     • Yield
       • A measure of the fraction of defects removed before compile and test,
     • Productivity
       • It appears that higher yields are associated with higher productivities
     • Process
       • You should also generate benchmark statistics for groups of several programs that were developed with the same process.

5. Yield Management

   • Software process
     • Defect Injection
       • Basic Defect Causes
         • Education
         • Communication
         • Oversight
         • Transcription
         • Process
     • Defect Removal
       • Strategy
         • Approaches
           • Compound multiple defect removal phases
           • Evaluate the cost and removal efficiency
           • Measure, analyze, and manage these removal phases
           • Initiate a defect prevention process
   • #Defects
     • The final number of defects, is the residual of the yields of all the process phases.
   • YIELD SPECIALIZATION BY PHASE
     • Consider:
       • High-level design review
       • Detailed-level design review
       • Code reviews
   • UNIT TESTING
     • Testing must be part of every software quality strategy
     • You can devise comprehensive tests for your program logic.

6. Defect Prevention Strategies

   • Focus on certain defect types:
     • Found in final program test or use
     • Occur most frequently
     • Are most difficult to find and fix
     • You can quickly identify effective preventive actions
     • Those that most annoy you

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