Matt Berther points to a thought-provoking entry by Christopher Hawkins who knows how to produce an accurate estimate and shares what to avoid when doing the estimates for a project….

First off, thanks for the mention.

Second, I agree with you on this bit:

“It’s not necessary to have a complete functional specification prior to starting development of an application. Using XP, there is a consensus on a small set of functionality that will be delivered (the simplest thing that could possibly work) and those requirements are generated. If these requirements are inadequate or unclear, then immediate clarification is obtained from the customer, so that work can continue.”

I usually outline the overall application and then develop detailed specs for one feature or task cluster at a time, making sure it is as unambiguous as possible before proceeding.

Now, I’ll admit that I would prefer to be able to spec the whole system up front, but I’ve found that even with the most diligent requirements gathering practices, clients invariably have epiphanies along the way that change the way they want to treat business processes, which of course means they want to change the tools supporting those processes.

Thanks again. I’ll be reading your blog. ;)