Thursday, 6 December 2007

How do you measure the good?

Well a new week a new topic. I've not finished with the Java stuff, but something else is nibbling at my consciousness. It is vaguely related to the previous blogs. The question I'm going to spout about today is "How do you measure the good?"

Having read "Zen and the art of motor cycle maintenance" [and "Zen and the art of archery"] I'm of the opinion that you cannot easily measure or quantify good (or quality, or excellence, or angles). But we all seem to know what is good when we see it. That.. TV program is good, that dinner is good. That film is good. When you push someone to explain WHY it was so good, you get rather less than quantifiable answers it made it made me laugh, it was tasty, I enjoyed it. In essence not very objective quantities, but certainly positive subjective comments.

This spin on quality ( .. as more than eloquently expressed in Zen & bikes book above) is not new. But it was not until a recent project that I realised the reason you can't quantify how good something is is because you can't count the number of good points. .... BUT you can count the bad points, moreover, you can count specific bad points. Say number of spelling mistakes in a text, and add this to number of words and bingo you have a spelling error rate (e.g. 1 spelling mistake per 100 words or 5 spelling mistakes in the 500 word article).

So let us assume that we want to measure the quality of a text and decide to count number of spelling mistakes, the number of grammatical errors. Lets say we now have an article which scores zero on those counts .. does that make it a high quality article? Does it make the article inherently good? Interesting? compulsive reading? The answer to that is obviously no. But then again these are characteristics of high quality writing. That said, if an article is well written with respect to grammar and spelling it obviously means that the author has taken more than a passing interest in the subject, and so has a fair chance of grabbing your attention.

If we move onto code quality.. told you this was related to Java. I know I'm on a loosing footing if I talk about code quality, so I'm going to change the rules (sign of a cheat!!). For the sake of argument I will not call it "code quality" I will call it "code QQnty". QQnty is like quality, but is a lot more quantifiable. QQnty will have a value, or set of values that you can point at and measure. You can take someones product and say it has a QQnity of X and someone else's product and say it is X+1. To judge if a piece of code is quality code is far too subjective, rather you will need to measure its QQnity. What you want to measure the QQnity against is an open question, but none-the-less, once defined the QQnity of that code will be a measurable number. The reason for this is that judging code quality is far harder than judging the quality of a piece of writing, or how good a film was. The reason for this is two fold
  1. Code developers are a mixed bunch of people, and the chances of any two of them agreeing on any subject, trivial or not, are about as slim as winning the lottery. It does happen, to someone, but I've never witnessed it first hand
  2. Code developers are generally quite passionate about their art (science). Anyone who may have even the slightest difference of opinion from themselves is a heretic. Heretics must die, or at least be argued with.
But there is one extra objective measure that can be performed with code... does the code work in the way it was intended (irrespective of the quality of the underlying code base). If the answer to this is yes, then you are home and dry. So if you define QQnity as the number of functional points (or requirements) minus say the number of bugs since release. Now you have quantified the code..

Well that is at least the theory, when you think a bit harder about it QQnity will itself become a subjective measure as different people will put different models together to measure what they want. What is interesting (to me anyway), it is extremely difficult to measure the good in a piece of code, but much easier to count bad points...
  • number of bugs (# bugs).. this is certainly a quantifiable point, how bad each bug is may or may not be quantifiable, but each bug counts as one.
  • number of functional points achieved/failed (FPA/FPF). it is more usual to use the failed version as there are fewer to count. Again, how important each functional point is is subjective, but you can count it
  • number of lines of code (LOC). This is very misleading. A large code base may mean that the code is highly complex, but it also probably means it is inflexible, or difficult to maintain. Similarly it could be lots of lines of junk. However, a measure none the less.
  • number of passed/failed tests (# PT/ # FT). Again the negative is more common than the positive
With the exception of number of lines of code (LOC) the above is mostly counting poor/failed points. To my mind LOC is a necessary measure, but should not as an absolute measure, and when used used as a denominator

QQnty = total FP/LOC
This measure means that if you succeed in producing the total functional points in fewer LOC, then you do better!! This may lead to more code re-use (should not impact LOC), simpler code (one hopes)


QQnty = total tests/LOC
This way the programmer can either increase total tests, or reduce LOC, either way both would likely (but no certainty) improve quality

However, watch out for .. QQnty = # bugs/LOC
This way the only way to improve (well reduce) QQnty is to increase LOC

This is the end of my splurge, now you've reached the bottom of this text... you can go to bed/work/school satisfied you completed one task today (but how good it is is subjective, but it still counts as one!!)

No comments: