Minimum standard - SML3
Expected standard - SML4
Excellent standard - SML5
SML1 - Initial usability: There is evidence that the application was created with no designs or consideration for organising it in terms of functionality for modularity or use. It may have been a demonstrator or pilot project.
SML2 - Use is feasible: There is no distinction between generic and solution-specific functionality. If available, the source code is organised into a primary system that provides general functionality and one or two subsystems that each provide multiple, unrelated, functions. Code within each module contains many independent logical paths. The architecture is closed with only a few internal functions accessible by external programs through the primary system.
SML3 - Use is possible by most users: There is evidence that the architecture is open, with full structuring into individual components that provide functions or interfaces to outside entities (i.e., open architecture); internal functions or interfaces documented, but not consistently; modules have been created for generic functions, but modules have not been created for all of the specified functions. Code within each module contains many independent logical paths.
SML4 - Software is usable: There is clear organisation of all components into libraries or registries with consistent documentation of all libraries as APIs or standard web service interfaces. Modules have been created for all specified functions and organised into libraries with consistent features within interfaces. Code within each module may contain many independent logical paths.
SML5 - Demonstrable usability: It is evident that all functions and data are encapsulated into objects or accessible through web service interfaces. There is consistent error handling with meaningful messages and advice, and use of generic extensions to program languages for stronger type checking and compilation-time error checking. Code within each module contains few independent logical paths.