I wrote a blog post a while back (http://webbindustries.com/archives/2010/10/index.html#e2010-10-19T10_29_00.txt http://webbindustries.com/archives/2010/10/inde

I wrote a blog post a while back (http://webbindustries.com/archives/2010/10/index.html#e2010-10-19T10_29_00.txt http://webbindustries.com/archives/2010/10/index.html#e2010-...) about Big Design Up Front and why it doesn't work. This touches on what you're describing; accurate estimation is possible when you're in a 'Manufacturing' mode and creating one more of something you've created many times before, but it's not possible when you're in 'R&D' mode creating something new or investigate a previously unknown bug. The theory behind BDUF is that you can come up with an accurate design, then come up with an accurate estimate for constructing the design, then go build it. It doesn't work because most software development is done in R&D mode, which you can't design or estimate accurately.