Attribute Wildcard Intersection

Hello again,

The following rule in "Schema Component Constraint: Attribute Wildcard 
Intersection" seems strange to me:

3 If either O1 or O2 is a pair of not and a value (a namespace name or 
·absent·) and the other is a set of (namespace names or ·absent·), then 
that set, minus the negated value if it was in the set, minus ·absent· 
if it was in the set, must be the value.


I don't understand the rationale behind "minus ·absent· if it was in the 
set". This means that ·absent· is removed whenever it appears in the 
set. It would be natural to remove it iff the second component of the 
"not" pair is ·absent·. Is it a bug the spec ?



Also, this rule:

6 If the one is a negation of a namespace name and the other is a 
negation of ·absent·, then the one which is the negation of a namespace 
name must be the value.

seems rather non-uniform (in particular because of rule 5). It breaks
the fact that the definition indeed defines set-theoretic intersection 
of sets of possible namespaces.


Finally, rule 5 is:

5 If the two are negations of different namespace names, then the 
intersection is not expressible.

What should an XML Schema parser do in this situation ?  I cannot find a 
constraints which ensures that this situation cannot happen.



Thanks !


   Alain Frisch

Received on Monday, 9 May 2005 17:52:08 UTC