Best RNG checking tools

Hi,

I was wondering if this list had any advice on a good RelaxNG checking 
tool. So far I've fed the RNG to a validator and seen if that worked, 
but I'd like to know if there's anything that will look in depth at a 
schema and tell me if it's any good, possibly with warnings about things 
that might bite me down the road, that aren't considered good practice, 
etc. I guess I'm looking for rng-lint or something along those lines.

I don't care about the platform so long as I can run it on OS X or 
Windows without too much hassle.

Thanks!

-- 
Robin Berjon