Architecture Quality Attributes

Intro

• Qualities that must be accommodated in a systems architecture over and above basic functionality.
• Categories of quality attributes:
  • Observable attributes. e.g:
    • Performance
    • Usability
    • Functionality
    • Security
    • Availability
  • Unobservable attributes. e.g:
    • Modifiability
    • Reusability
    • Testability
    • Portability
    • Certifiability
  • Business attributes.e.g:
    • Time to market
    • Overall cost
    • Longevity
    • Backward compatibility

Quality Attribute Scenarios

• Meaningless to say System is modifiable, reusable etc. How do we justify it ?
• Quality Attributes are best characterised via scenarios.
• SEI format for QA scenarios:
  • Source of stimulus
  • Stimulus
  • Environment
  • Artefact
  • Response
  • Response Measure

• General QA scenarios: These scenarios are system independent and can be applied to any system.
• Specific QA scenarios: These scenarios are derived from the general scenario by instantiating each part.