ORA-DM-NONEMPTY

*Data Model, Section 4.1.1 base-uri Accessor*
third para: "If the base URI property ... is non-empty"
The Infoset recommendation does not have a notion of a property being 
"empty" or "non-empty".
It does have the notion of a property being "unknown" or "no value". The 
Infoset recommendation says that "unknown" and "no value" are different 
values, but it does not indicate whether the value of a [base URI] 
property may be either these values or just one of them. Anyway, you 
probably mean these values when you say "empty".

Does "empty" mean "unknown" or "no value" ?
If so, it may be better to use the terminology in the Infoset 
recommendation.