If a musician has her instrument on hand, she can make music, every single time. Musicians are really quite reliable. Their improvisations and crowd-pleasers wo

If a musician has her instrument on hand, she can make music, every single time. Musicians are really quite reliable. Their improvisations and crowd-pleasers won't all be as good as the best works of Mozart, or Monk, or even Billy Joel, but chances are that the crowd will be at least moderately pleased. Cover bands do not routinely run 300% over budget and six months late, and if they do you can be confident that the fault was entirely theirs -- it's not that the gig, which seemed simple on the surface, turned out to be completely intractable. A skilled carpenter or vacuum-cleaner engineer might not produce a masterpiece every time. But the result will probably be a house that doesn't fall down, or a thing that picks up some dust for at least a little while. Vacuum cleaners are a well-understood technology, and while carpentry projects do occasionally go nonlinear (if you change the specs mid-project, or a freak windstorm blows up, or they discover a natural spring while digging your basement, or... well, just go read Mr. Blandings Builds His Dream House, one of the greatest engineering books of all time ;) they are nonetheless relatively predictable, and the more experienced the carpenter the fewer surprises you can expect. Now go read Dreaming in Code, which shows that even if you are Mitch "I Built Lotus" Kapor and you hire Andy "Mac OS 1.0" Hertzfeld your software project may fly straight into a wall: You may blow the schedule by a factor of five, and the budget by a factor of ten, and still not ship anything. [1] It has happened. People who write books about corporate IT throw around numbers like fifty percent when discussing the odds that a given software project will succeed. And the reason why programmers don't stop talking about this is that it is vitally important that our clients understand the risk in advance! Which they often don't. Nothing in their everyday experience with plumbers, dentists, and caterers has prepared them for it. --- [1] Note: These numbers are not the ones from Dreaming in Code. I made them up. ;) I actually have yet to finish Dreaming in Code. It induces painful flashbacks.