Peter Dängeli

Sorry, I lost sight of this. If a solution to the problem is too intricate and given that as-is a relatively clear error message is output on the command line,...

Ok, that makes sense. But an attribute in a namespace should generally be able to co-exist with an unqualified one of the same _local-name_, shouldn't it?

Thank you for testing, @jamescummings and @lb42. Perhaps the [problem pointed out by @lb42](https://gist.github.com/jamescummings/155429676474d9416b8251c717776657#gistcomment-2023591) is related to `mode="add"`. I left this out in my ODD (which is very close [to...