Requirements Classification

  • performance.
  • portability.
  • security.
  • learnability.
  • availability.
  • maintainability.
  • reliability.
  • robustness.
  • memorability.
  • testability.


measures the time required to make a new user become skilled in using a particular software product.


means how convenient the software is to help a user improve his productivity.


refer to how quickly a user can pick up his knowledge about the software product after a period without using it.

Error rate

means how many errors a user may make when performing his/her tasks.


represents how willing a user may be to use the software product.