When to use iterative development? You should use iterative development only on projects that you want to succeed.

Why is composing symphonies tough? I don't know. It's just very few people in the world can do it well. And I think that's the case with upfront design. It is very hard to do well.

If you're afraid to change something it is clearly poorly designed.

When you actually sit down to write some code, you learn things that you didn't get from thinking about them in modeling terms...there is a feedback process there that you can only really get at from executing some things and seeing what works

Now I'm a pretty lazy person and am prepared to work quite hard in order to avoid work.

One of the big dangers is to pretend that you can follow a predictable process when you can't.

One of the things I've been trying to do is look for simpler or rules underpinning good or bad design. I think one of the most valuable rules is avoid duplication. "Once and only once" is the Extreme Programming phrase.