Tonights Topic: Moving Toward Quality

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Tonights TopicMoving Toward Quality
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Where Are We?

• Three aspects to this course

Design
Assessment
Improvement
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Quality Through Design

• Quality software always requires a quality design
• We have already explored some key design issues
• We will return to design at times
• But well move on to

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What Is Assessment?

• Measurement to
• Gauge degree of quality
• Spot weak points
• Target improvements
• Track changes
• Can be quantitative or qualitative

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What Is Improvement?

• Plans/strategies/techniques to increase quality
• Should target specific ilities that are
  important for project
• Rely on assessment to gauge effectiveness of
  changes

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Assessment and ImprovementAre Intertwined

• Improvement requires measurement for tracking
  success
• Measurement identifies weaknesses, leading to
  improvements

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Main Assessment Techniques

• Reviews
• Standards
• Metrics
• Testing

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Recall the Definition of Quality

• A set of attributes software should have
• ilities
• Most ilities are not directly measurable in
  practical terms

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Robert Glass Defines Quality

• Good quality software has

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Three Recurring Quality Lessons

• Requirements are the foundation
• Dev. standards guide process deviation decreases
  quality
• There are implicit requirements that often go
  unstated

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Difficulties With Requirements

• Spec is often oriented to customer needs, but
  developer may have requirements too
• Some characteristics cant be specified
  unambiguously
• Specs are usually incomplete

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Difficulties With Process Conformance

• Process quality is very important, but
• Changing the process doesnt necessarily improve
  product
• External factors also affect quality
• Individual skills/talents are critical

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A Word About ISO 9000

• International standard for quality management
  across industries
• ISO 9000 is a set of standards applicable across
  large range
• ISO 9001 is most general of these, applicable to
  software orgs

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ISO 9001

• A generic model of a quality process
• Defines process, as well as necessary standards
  and procedures that should exist
• Specifics arent defined in detail
• Defined and documented in org.

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ISO 9000 and Quality Planning
ISO 9000 quality models
Organizational quality process
instantiated as
documents
instantiated as
Organization quality manual
Project quality management
used to develop
Project 1 quality plan
Project 3 quality plan
Project 2 quality plan
supports
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Organizational Quality Manual

• Documents quality plan for that organizations
  products
• Selects those organizational standards
  appropriate to projects and processes at hand
• Typically, quality group is separate from
  development team

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McCalls Quality Factors
Maintainability Flexibility Testability
Portability Reusability Interoperability
Product Revision
Product Transition
Product Operation
Correctness Reliability Usability Integrity
Efficiency
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Choosing Quality Factors

• McCalls diagram helps organize them
• But for any project, one needs to choose which
  are important
• Checklist for software quality

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Most Guidelines Are General

• Many quality standards and checklists of quality
  factors
• Most are very generic
• Any can be debated endlessly
• Only agreement it should be tailorable to
  individual projects

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Quantifying Quality

• Goal precise, reliable measures
• Many ilities are difficult to measure directly
• Instead, we indirectly measure using indicators
• The hope many independent indicators provide
  confidence

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Criteria For Effective Metrics

• 6 simple criteria for good measures
• Simple and computable
• Empirically and intuitively persuasive
• Consistent and objective

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Criteria for Effective Metrics (cont.)

• Consistent in use of units and dimensions
• Progamming language independent
• Effective mechanism for quality feedback

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A Scenario About Measurement

• You cant just collect data
• You have to know how to interpret it
• Here is a scenario to avoid

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Scenario The Hypothesis

• A manager wants to improve quality
• Decides to monitor of change requests submitted
  by customers
• Assumes change requests are related to
  usability/suitability
• More requests less quality

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Scenario The Improvement

• Handling change requests is expensive, so
• Company decides to modify process to increase
  customer satisfaction
• Intent better quality, fewer change requests

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Scenario Process Changes

• Process change more customer involvement in
  design
• Customer beta testing of all products
• Fast incorporation of customer-requested changes

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Scenario The Results

• New products using this process are delivered
• Some trigger fewer change requests, some trigger
  more
• Manager doesnt know what to conclude about
  change in quality why?

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Scenario Possible Causes

• Many causes for change requests
• Doesnt meet customer needs
• Very good, widely used, so customer needs
  change/expand
• Responsivens of co. leads to customer confidence
• More thorough testing

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Scenario Conclusions

• We cant conclude much from the measurements
• Too many causes intertwined in one measurement,
  so we cant tell which one(s) are the source