Re: Just one side
the difference from formal specification in waterfall is that it focuses on "what it needs to deliver" rather than "what the design should look like". The specification should always focus on what it needs to deliver for all methodolgies. A good specification is an essential requirment because without it how does anyone test whether the system is working correctly? Most agile projects seem to think a good specification is not needed.
My experience of agile is when 'successful' it is becaus the agile evangalists have managed to convince those that matter that what would have been considered abject failure, huge delays, fragile SW, massive overspend, final SW which does not deliver key functionality, constant bug fixes as being an inevitable part of the process.