The ISO 9241 defines usability as
"The effectiveness (accuracy and completeness to reach a goal), efficiency
(resources expended), and satisfaction (comfort and acceptability to users)
with which specified users achieve specified goals in particular environments".
Usability promotes three basic principles:
- Learnability: The ease with which new users can begin effective
interaction and achieve maximal performance.
- Flexibility: The multiplicity of ways the user and system
- Robustness: The level of support provided to the user in
determining successful achievement and assessment of goals