on software quality - chapter 2
TRANSCRIPT
Software Quality Assurance
Chapter II: Basics and Definitions
Christian Soltenborn
FG Database and Information Systems
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Overview
What is software?
What is quality?
Views of quality
Why does the classical approach to QA not apply?
Basics and Definitions
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Basic Terminology
Software is:
Computer programs, procedures, and possibly associated
documentation and data pertaining to the operation of a
computer system.
[IEEE_Std_610.12-1990]
What is Software?
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IEEE
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IEEE Standards Association
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Software Quality - IEEE
Software quality is:
(1) The degree to which a system, component, or
process meets specified requirements.
(2) The degree to which a system, component, or
process meets customer or user needs or
expectations.
[IEEE_Std_610.12-1990]
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Software Quality – More Definitions
Software quality is :
„The ability to satisfy stated or implied needs“ [ISO 8402]
„A product or service free of deficiencies“ [American Society for Quality]
„Conformance to explicitly stated functional and performance
requirements, explicitly documented development standards, and
implicit characteristics that are expected of all professionally
developed software.” [Roger Pressman]
„Fitness for use“ [Joseph M. Juran]
„Degree to which a set of inherent characteristics fulfills
requirements“ [ISO 9001]
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Overview
What is software?
What is quality?
Views of quality
Why does the classical approach to QA not apply?
Basics and Definitions
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Basic Terminology
The view of quality can differ upon:
The user
The context
The product alternatives
The stage of the lifecycle
[…]
What is quality of a product?
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Different views of quality
Product view: the quality of a product is measurable in
an objective manner
User view: quality is fitness for use
Manufacturing view: quality is higher if product is
easier to produce
Value-based view (Economic): quality is a function of
costs and benefits
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Overview
What is software?
What is quality?
Views of quality,
product quality,
…
Why does the classical approach to QA not apply?
Basics and Definitions
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Why does the classical approach to QA not apply?
Requirements:
define complete set of external quality characteristics
complete set of internal quality characteristics and a detailed and complete set of requirements and specifications
Design:
design that satisfies the requirements and specifications
design for reliability (wear out)
design for manufacturability
design for maintainability (e.g., self-diagnosis)
Manufacturing:
statistical production process control with acceptance sampling
focal area of quality assurance!
Operation: collect failure data for continuous improvement and predictions
(intelligent maintenance)
Classical approach (from hardware design)
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Why does the classical approach to QA not apply?
Invisibility of the product
Limited opportunities to detect defects (“bugs”)
Often new demanding functionality has to be realized
Often software has to realize extraordinary high
complexity
[D. Galin, Software Quality Assurance: From theory to implementation.
Harlow, England: Pearson Addison Wesley, 2004.]
What is special about software?
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Why does the classical approach to QA not apply?
Requirements:
Completeness is hard to achieve (complexity, development process)
Design:
design for reliability only in special cases
design for manufacturability is not required
focal area of software quality assurance!
Manufacturing Implementation:
limited success with statistical process control (metrics)
Operation:
fixing bugs found
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Quality Models
Old-fashioned methods for quality assurance don’t work
with software
The general definitions of software quality are not
sufficient in practice
Thus, a standardized quality model is needed!
Current Standard Quality Model:
ISO/IEC 9126-1: Software Engineering – Product Quality, Part 1:
Quality Model, 2001
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Now: Quality Standards!