RuleofThree

The Rule of Three (ref Jerry, but I don't remember which book) is this:

One alternative is a trap.
Two alternatives is a dilemma..
Three alternatives provides you a choice.

And, once you've gotten to three alternatives, you can generally develop numbers 4 and more fairly easily. When you have to develop three alternatives, you show you understand the problem. With understanding comes the ability to select from among the alternatives.

When I'm managing a project where there's an architecture phase, I ask the architect how many alternatives he/she has developed. I ask what three things can go wrong with each architecture. Now, we can have a discussion about the architecture that is closer to reality.

With project planning, I ask people for alternatives to organizing the project, especially if they're stuck in implement-by-architecture thinking.

Jerry, if you remember which book you wrote the Rule of Three in, please say so. -- JohannaRothman 2005.03.29

It appears in several contexts in different books. You've stated the general rule of three, but specific applications are found in such places as:

Think of three things that can go wrong with your design.
Three design alternatives.
Three things that could go wrong with your decision.
Three things that could mess up your project plan (risks!).
Three decision alternatives.
and many others

It's definitely a stop-and-think rule. That's the essence. I can't prove that thinking is better than not thinking, and I suppose I can come up with three situations where thinking gets you in trouble, but in general, I believe that you improve your chances if you use your brain. - JerryWeinberg 2005.03.30

Updated: Thursday, March 31, 2005