Going Over the Waterfall

One day Roscoe and I were walking across his backyard to toss a round of horseshoes. I had told him that even though I hadn't played in years, I bet I could beat him. "OK, now we'll see who's going to beat whom, Sonny," Roscoe said. "And before I teach you the right way to throw a horseshoe, I'm going to demonstrate to you why waterfall development is doomed to failure."

I had to smile. Six months ago, I was the one who wanted to talk about software development. Now it was Roscoe who kept bringing it up. Always on the prowl for new ways to look at things, I was eager to see what he had to show me.

When I picked up my pair of horseshoes, I suddenly realized that the big, omega-shaped things were heavier than I'd remembered. "C'mon, get ready," Roscoe ordered. "There's the stake. See if you can hit a ringer on your first toss."

Naturally, I felt a little pressure after my bragging. I swung the horseshoe a bit, back and forth, getting a feel for it, then took one big swing. Of course, I didn't hit the stake. I didn't come anywhere near it, in fact. My horseshoe just bounced away and landed about 15 feet from its target.

"No fair!" I exclaimed. "You need to let me have a few practice throws."

If you are unfamiliar with horseshoes, it is normal to take several practice tosses before you get competitive. It's like anything else, really. You need to get used to your equipment, which in my case was an arm that hadn't seen a lot of exercise lately. "Well," responded Roscoe, "that might or might not help, because you missed for three reasons. First, as you point out, the target wasn't where your arm thought it was, due to some miscalibration.^[3] Second, you will always have some imperfection in your execution; none of us is perfectly steadythe horseshoe doesn't always go where we aim it. And third, between the time you let go and the time the horseshoe hit the ground, the stake moved!"

^[3] It turns out that there were two very good reasons for my "miscalibration": Roscoe's horseshoes were a little heavier than the normal set, and his distance between stakes, end-to-end, was a little longer than the standard setup. Both of these were small effects, around 10 percent, and hard to discern immediately, but they led to the target "not being where I thought it was." This is why warm-up tosses are so important: Your mind-body computer makes adjustments automatically after some practice throws.

"Bull bleep," I responded. "Nobody moved the stake."

"True enough, but after you let that horseshoe fly, there was an instantaneous gust from a 40mph crosswind that you hadn't taken into account. The effect was the same as if someone had moved the stake in the opposite direction," Roscoe replied. "Plus, any angular deviation is multiplied by the distance the horseshoe has to travel, so it is no wonder you failed."

"Well, at least in project management, I don't have to score a ringer every time," I said.

"Fair enough," responded Roscoe. "That's where the expression 'Close only counts in horseshoes and hand grenades' comes from. 'Close enough' is often just fine in project management. What really hurts is missing the target by a wide margin, especially after your 'horseshoe' has been in the air a long time. Yet, this happens all the time with the waterfall approach, because you only get one toss. And typically, just as in horseshoes, there are three critical problems at work:

• The target isn't where you perceive it to be.

• You make human mistakes in your execution.

• The target moves, to boot."

It made sense. Taking one shot at anything seemed silly. But I thought I would tease Roscoe a little by taking a completely contrarian position.