Loose coupling in complex systems is almost universally regarded as a good thing. So I've been surprised how often and how vigorously we have had to defend the system we're developing from other systems wanting to access our private parts.
Problems caused by tight coupling are not restricted to IT systems. Two recent incidents reminded me of just how important it is to think very carefully before introducing unnecessary coupling in any complex system.
A colleague, lets call him Pontus, was travelling to work in his new car when it came to an unexpected standstill. Now this particular model has a feature which reduces the engines effect as it starts running low on fuel. But Pontus hadn't run out of fuel; the petrol gauge had malfunctioned. Normally not a critical problem, unless the petrol gauge is coupled to the engine ...
This type of problem doesn't only affect cars; trains are also susceptible.
Last week I was travelling to work by train when it came to an unexpected standstill. A toilet malfunction was immediately suspected. Now a dodgy toilet would not normally be a critical problem, unless the flush uses the same vacuum system that powers the train's brakes ...
So beware of creating unnecessary coupling. You will regret it. Maybe not today, maybe not tomorrow, but soon and for the rest of your life.
