empty elements

The UBL 2 Specification disallows empty elements (the old IND5 and IND6 rule, now moved to UBL Spec).

Unlike the nillable attribute, this rule is not enforced by the XML schemas, at least not for string based data types. Shouldn't it be enforced?

I can see various options:
- a minLength facet (on UDT, or CBC?)
- and perhaps a pattern excluding blank strings

Or embedding it as a business rule, using Schematron.

Any views on this topic? Or have I overlooked something?

Regards
Juerg