Here's a quote from Scott Ambling that I think we all need to be able to respond to as convincingly:
Why is Big Modelling up front the wrong thing to do?
Mistakenly compare software development to civil engineering. A common analogy is to compare software models to architectural diagrams for a bridge or building. Unfortunately the analogy isn’t an accurate one: software is more malleable than concrete making it easier and much less expensive to change your mind part way through the effort; The material (app servers, operating systems, …) used to build software isn’t as well understood as the material to build bridges (steel, concrete, …) making it much more difficult to accurately plan up front; Incremental delivery often doesn’t make much sense when you’re building a bridge, so what if the foundation has been set but the rest of the bridge isn’t in place, although incremental delivery of software is clearly possible and as I argue above the norm. Much better analogies are comparing software developers with chefs or comparing software development with putting on a play (as described in the wonderful book Artful Making).
Read more on Scott's article on why Big Modeling Up Front is an Anti-Pattern
