I’m sure there are plenty of definitions of redundancy. A naïve definition might just try to make it a synonym for duplication.
Duplication isn’t really a problem, though. Certain acts of duplication are the cause of certain redundancies – for instance, copy-pasting a method – so it’s natural for us to blame duplication for our problems.
Yet, even though it is sometimes the cause of a problem, duplication is not, in and of itself, a problem.
The problem exists when you need to make the same change to two or more things. Specifically, it’s a problem when you need to find two or more places to make the same change. The reason why it’s a problem is that you run the risk of missing one of the places where you need to make a change and you almost certainly will expend a lot of energy trying to mitigate that risk.
More on this to come.
