> What's exactly is the problem with division before I go off 
> thinking that all is home and hosed with xs:decimal?

What's the result of 10 div 3? The spec allows both 3.3 and
3.33333333333333333333333333333333333333333333 as legal answers. However,
you have a reasonable expectation - not a guarantee - of at least 18 digits.

Michael Kay
http://www.saxonica.com/