Software%20Quality%20Concepts

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Software Quality Concepts

• SWENET Module SQA1

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Software Quality Topics

• Defining software quality
• Attributes of software quality
• Quality trade-offs
• Quality attributes in requirements definition

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Software Quality

• What is quality?
• In general
• In business

?
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Definitions Quality is...

• Quality is fitness for use (J. Juran)
• Quality is the most profitable product line we
  have (H. Geneen)
• Quality is free (P. Crosby)
• Quality is compliance to a standard(W.E. Perry)
• Quality is a degree of excellence(R. Glass)

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Quality Concepts

• Cost effective investment
• Relative / Absolute
• Within a Context?
• Cadillac versus Chevrolet
• Compared to some standard
• Measurement and analysis implied
• An intangible

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Definition Software Quality

• What is software quality?
• What are the attributes of quality for software?

This is high quality software because...
?
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Software Quality Attributes
Portability
Efficiency
Testability
Reliability
Understandability
Usability
Modifiability
(Boehm, 1978)
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Software Quality Attributes
Usability
Functionality
Performance
FURPS
Supportability
Reliability
( Grady / Hewlett-Packard)
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Software Quality Attributes
Product Transition Portability
Reusability Interoperability
Product Revision Maintainability
Flexibility Testability
Product Operation Correctness Integrity
Reliability Usability Efficiency
(Cavanno and McCall, 1978)
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Software Quality Attributes
FURPS
Boehm
Cavanno/McCall
Reliability
Reliability
Reliability
Performance
Efficiency
Efficiency
Integrity
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Trade-offs and Quality

• Software engineers must make trade-offs on many
  levels and quality is no exception
• Quality compromises include
• Trade-off among quality attributes
• Trade-off of quality for other factors

Discussion What trade-offs (including quality)
might affect a choice to purchase one of the
following - Luxury sedan - Low end compact
- Pick-up truck
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Tradeoff Among Quality Attributes

• Attributes often conflict
• Ref Glass

Portability
Efficiency
Usability
Understandability
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Trade-off of Quality for Other Factors

• Quality competes with other demands
• Short term vs. long term effects

Quality
Cost
Time