I'd be interested in taking this. I've contributed before though so if you want someone new to take this totally understand.

@DCtheTall -- no worries, please take it up.

Been looking into this some, and while I have an idea of where to start, it turns out the definition of these is quite broad. This might be more complex than I anticipated.

This link also provides some useful documentation including what ranges of Unicode values are allowed for this type.

So far here are some "base case" rules I have learned:

• xsd:anyURI strings ignore any leading or trailing whitespace, so the first thing we should do after asserting the input is a string is call trim().

• An empty string is valid, so we check for that. As far as I can tell from the docs, there is no upper bound on the length.

• We can then check that each character is in the ranges specified in the link above.

• Any URL is valid, so we can use isURL to check for those.

Still doing some research, but I would definitely appreciate any pointers. Like I said, it turns out the definition for these strings is actually pretty broad.

One alternative we could consider is adding a function which validates International Resource Identifiers (IRI), which are also mentioned in the link I provided.

@profnandaa any ideas on how to go forward with this? I admit I am a bit stuck given how broad the definition of this string type is.

@DCtheTall -- I'm very sorry I missed on this reply... Perhaps we just add an enhancement/option on isURL to support this?