Both are fine, it's something most people will never use (I don't propose making in an RcParam) - its for follow on applications (which I plan to look at in the next couple of weeks) for which I will want to implement a namespace. The one thing in favour of this approach is that there is no ambiguity - if you get it wrong then you will get a decent message about it, but I can also see the other side of the argument too (if you can check that something is wrong, you can fix it programatically for the user...)