These are some really good design principles. It is very nicely explained. I preferred following this guide than understanding Rails scafolding. With Java being such a verbose language I felt this was mostly written for Java based application, I preferred this explaination and apply it to RAILS and how it was done there. Sometimes it is frustrating why a specific scaffold behaves in the way it behaves in RAILS. That to say am no way a awesome ruby rails developer. But this link and guide provides industry best practice and reason for it. Good read and nice blog to follow. Link