> Thanks for the reply. As far as I can see in the W3C Schema
> definition, things are simple -
> decimal numbers use decimal points, and no option seems to be present
> for allowing
> decimal commas. ( at least the regular expression in the  w3c docs is
> definite about that).
> It _is_ the simplest solution.

For data interchange purposes, you want to pick *one* convention. No 
matter which one you pick it's going to disappoint someone, so the 
question winds up being which one's natural for the folks writing the 
spec. And since most spec authors are programmers and most programmers 
(and languages) already expect . as the decimal separator...  More 
directly: There was an existing standard Schema could reference, so they 
referenced it rather than reinventing the wheel.

Of course user interfaces are free to render the data in other ways. And 
you can use the other convention in XML if you're willing to be 
nonstandard or to simply treat it as text rather than expecting other 
tools to recognize it as the intended number.

(Someday I should look up how , and . wound up with their functions 
being swapped in some cultures, and check which convention is actually 
older... just for historical interest.)