An alternative to SOLID when the problem is not clear enough to get to a sound design.
I assisted this video. It is an alternative to the SOLID design principles. Although I prefer SOLID as it provides prescriptive criteria to good design, this CUPID provides a more goal oriented approach to design. So, when the problem is not clear enough to get to a design that meet your needs you can follow this CUPID approach and throughout refactoring incrementally improve on the design.