Minimum standard - SML1
Expected standard - SML3
Excellent standard - SML5
SML1 - Initial usability: The software and software development process comply, at least in part, with locally defined standards and best practices. The standards may be internally or externally described, but are implemented with modifications to meet local conditions. There may be little or no documented evidence of standards used, but it may be possible to infer this from the software consistency of functionality and interfaces.
SML2 - Use is feasible: The software and software development process endeavour to comply with recognised standards or widely used best practices, but without verification or testing. There is some documented evidence that standards are used, but it can not be verified.
SML3 - Use is possible by most users: The software and software development process comply with open, recognised or proprietary standards, but there is incomplete verification of compliance. Compliance to recognised standards has been tested, but not for all components.
SML4 - Software is usable: The software and software development process comply with open,recognised and/or proprietary standards. Compliance with these standards has been verified through testing for all components. Documented evidence for selected standards and verification through testing is available.
SML5 - Demonstrable usability: Compliance with open or internationally recognised standards for the software and software development process, is evident and documented, and verified through testing of all components. Ideally independent verification is documented through regular testing and certification from an independent group.