Requirements and Specs Are Always Ambiguous

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UPDATE: As an aside, it would probably be more accurate to say the FizzBuzz question is a Requirement. So where you read the term Spec, you can replace it with Requirement. Either way, the same thing applies. The only thing not ambiguous is the code. As they say, the code is the spec.

One last point, then I’m done with this topic of FizzBuzz and spec writing. In a recent post, I mentioned tongue firmly in cheekthat the FizzBuzz “spec” has certain flaws. Now I admit I’m taking this out of context a bit to make a point. FizzBuzz is an simple interviewquestion, not a spec, possbily intended to elicit this type of analysis from the candidate. Even so, I think there’s a good lesson to learn here.

My point was that all specs are merely rough approximations of the actual requirement. Specs are ambiguous, but software is not. Software doesn’t generally deal well with ambiguity. Change a random bit in memory and all hell breaks loose.

However, some of that was lost due to the extremely nitpicky point I made about the spec. So here’s another, still nitpicky, but a bit less so.

Every so called “correct” program written in the comments of Jeff’s blog had the following output.

1
2
Fizz
4
Buzz
Fizz
7
Fizz
Buzz
11
Fizz
13
14
FizzBuzz

But, doesn’t the following output meet the letter of the spec (difference in bold)?

1
2
Fizz
4
5Buzz
Fizz
7
8
Fizz
10Buzz
11
Fizz
13
14
FizzBuzz

My point being, the spec is explicit about replacing numbers divisible by three with “Fizz”, but it doesn’t say to replace numbers divisible by five.

Yes, I agree. Developers should not act like total logicians and nitpick every detail. Human language is inexact, and we have to deal with that fact of life. Unfortunately, sofware doesn’t have the same resiliency towards ambiguity. If this output was meant to be fed into another software system, this ambiguity would cause bad data, software crashes, who knows what calamity!

You might say I’m splitting hairs here. Of course I am because the compiler is going to split hairs. The Web Service I’m trying to call is going to split hairs. The HTML browser is going to try and not split hairs, but is going to ultimately fail. Software is all about splitting hairs.

Instead, we need to move beyond the spec and ask questions before writing code, during writing code, and after writing code. Do not be afraid to talk to the customer or customer representative. That’s all I was trying to say.

Thanks to Rob Conery who was trying to make this point in my comments, but it was lost on everybody. ;)

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