“Good fences make good neighbours”
It's an old saying, reminding us that to live together side-by-side you need to know where the boundaries lie, and who is responsible for what. Where there's room for dispute and argument, people will end up fighting.
At Tencastle, we say “Good interfaces make good partners”
It's the same principle. For systems to work seamlessly together, we all need to know who is responsible for what. Wherever boundaries are blurred or badly-defined, it's a major cause of system failure. Engineers know that the interfaces are where things go wrong.
Clear interfaces lead to a clear allocation of responsibility. If something goes wrong (with good testing) you can work out what has gone wrong and whose fault it is. This isn't necessarily about blame: it's about working out how to fix a problem quickly.