I think a lot of mature RFCs are based on prototypes. In my experience, prototyping is the first step in design; I know I've seen "designers" and "architects" h

I think a lot of mature RFCs are based on prototypes. In my experience, prototyping is the first step in design; I know I've seen "designers" and "architects" hide that they prototyped something before writing the document they've been asked to. I know at least one did this to give the impression that they were able to express it fully-formed from whole cloth. Sometimes you can get away with documenting a design based on prior art, but without creating your own prototypes. For the most part, rather than the first, good design documents are the the second or later expression of a design. Added: I think this ties into what jsty is saying. Good designs tend not to be the first iteration of an idea, regardless whether the iterations were intentional design, or refactoring. IIRC, Joe Armstrong (RIP) was a firm believer in the "write it once, then throw it out and rewrite it at least once" pattern of development. I think that whether you're writing a design document or a new version of some portion of code, you are refining a design, and that tends to help.