Wednesday, 3 June 2009

Evolving Design - Its a must!

A couple of days ago I read Gil's post about "Good Design Is Not Objective", in it he writes

So are there "good" or "bad" designs? Every person has an opinion. Opinions change over time. Problems and technologies change over time, and a design can help or interfere with the project, but you'll know that in hindsight.

Yesterday, at one of my client a simple question turned into a related discussion. One of the software architectures asked me if I ever saw (and what do I think of) a system which uses a global variable repository. One that every part of the system could use at will  to store data and is used as way of communicating between various parts of the system. Apparently that kind of an approach is used in their system and he wanted to know what I would say.

After thinking a little, I said that the only system which seems to me to be similar would be Windows registry, I said that I never encountered such a system in a project I was working on (at least not on the scale he was talking about). I also said that in my past each time I used such global variable (in a similar manner) I regretted it. And last that it really sounds like very "old fashion" approach to design. Something that kind of contradicts object oriented design.

The guy told me he said, that this part in question is very old and was written some 15 years ago when the company was at its startup stage. It appears that the entire system was evolved on top of it, which made it very hard to replace. in fact the cost was so high that each time someone considered it they decided to leave it as is.

Now I think this is a very interesting case that demonstrates how our continual search for the Best Design is just stupid.

There is no such thing as the Best Design!

Like most things, design also carries a context. In this case the current mechanism they have was (as the guy admitted) the quickest and cheapest way of reaching a product (one which people will buy). At that time (15 years ago) the technology (they were writing in C) and software engineering approaches were in line with such a mechanism. And it was a reasonable design at that point of time.

Is it still so today? absolutely not!

The company is no longer a startup, what was good at that time is really bad today. The needs has changed over time, the technology has changed over time, and the product has changed over time.

As Gil said it:

Time Changes everything

The Best Design today will probably wont be the Best Design tomorrow. A developer accepting that fact, can focus on producing a "good enough" design and evolving it as needed over time.

In my opinion that was the actual Mistake done. Its not that the design was wrong. its the fact that they assumed it wont need to change. That assumption made the cost of actually changing it high resulting in an unsuitable design they have today.


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