With the inclusion of MVC in Web-based design, the develope/Engineer have very less to worry about changes they have to incorporate in the later stages if the system is designed properly.This is what is guarnteed if the system is designed following a approach as approved by researches and OOAD implementor. The UML ofcourse is very strong modeling language I ever used, I stress using it fully to design a system so that lots of labour is decreased in the later stages of the SDLC.