xlink abuse, using an unknown scheme for macro language

Hi,

I have a number of personal schemes I've defined which I use to put
dynamic functions into XML documents via link semantics, for example
in open office, which can then be expanded by my interpreter.

So I was thinking to transport this to Xlink, but as I am not an
expert on Xlink, what does an Xlink processor do if it encounters an
unknown URI scheme?

Cheers,
Bryan Rasmussen