[platz]

sure, if you are trying to solve the fully parametric abstract equation over all possible inputs, which is precisely what I was saying to try to avoid.

In absence of a grand unified theory, tackle obvious concrete instances when they crop up.

If the different "simple" answers (which I am not sure exactly what that means) solve the problem, then I really do not care if there is some equivalence principle there; just pick one as long as it produces the concrete outcome that you want.

[sokoloff]

The problem can be roughly stated as: For a company registered in country I, selling product/service in country F, with inputs licensed from and/or created in countries N, U, B, G, A, and C, and costs incurred in a potentially different set of countries, what's the amount of tax due to each country represented in the graph?

There are many simple answers to that question; who gets to decide which simple answer is the one enacted? Countries F, I, and U are likely to disagree on which simple answer is "best", which is why we rely on laws and courts to frame and adjudicate the issue.