Having just worked on a data analysis that involved orthogonality, I just want to point out that "orthogonal functions" does not necessarily mean functions do one task, etc.

A set of orthogonal items means that between any two items, there is no overlap of their 'function'; for vectors in 3D Euclidean space, this means that no more than 3 vectors can be orthogonal to each other, and that for 3 vectors, they must be at right angles to each other.

In programming, this corresponds to functions having no utility that overlap. That is, if you have a function that reads, parses, and prints data, and another one that just prints data, these are not orthogonal.

Now, good programming practice, planning, and repeative refactoring are similar to mathematical tools that can help find the optimal orthogonal set of functions/vectors/whatever. That is, with programmming, several rounds of refactoring will help you to not only identify a set of orthoganal functions, but functions that also perform only small tasks such that they can be combined in some manner to do complex ones.

So while the statement above is not *wrong* per se, it's not entirely accurate, and I'm just trying to clear that up :-)

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Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain
It's not what you know, but knowing how to find it if you don't know that's important