Michael Leditschke scripsit:

>  The level of co-constraint checking offered by RELAX NG is an improvement
>  on their absence in XML Schema but is this more than leap-frogging? I would
>  also add that the situations where I needed co-constraints were often
>  content based, e.g. if element X contains "5", attribute Y should be
>  present.
>  I may have missed it, but the support in RELAX NG seems, by the nature of
>  RELAX NG, purely structural. 

Not entirely: in the case you want, RNG can cope.  Consider this schema:

element x {
	(attribute y {text}, "5")
	| (string - "5")
	}

Valid documents:

	<x y="7"> 5</x>
	<x> 4</x>

Invalid documents (Jing says "bad character content for element):

	<x> 5</x>
	<x y="8"> 4</x>

RNG, like XML, doesn't care about the order of the attributes in the instance.

An alternative schema that permits (but does not require) y to be present
if x is not 5:

element x {
	(attribute y {text}, "5") |
	(attribute y {text}?, string - "5")
	}

-- 
John Cowan <jcowan@[...].com>      http://www.reutershealth.com
I amar prestar aen, han mathon ne nen,    http://www.ccil.org/~cowan
han mathon ne chae, a han noston ne 'wilith.  --Galadriel, _LOTR:FOTR_

-----------------------------------------------------------------
The xml-dev list is sponsored by XML.org <http://www.xml.org> , an
initiative of OASIS <http://www.oasis-open.org> 

The list archives are at http://lists.xml.org/archives/xml-dev/

To subscribe or unsubscribe from this list use the subscription
manager: <http://lists.xml.org/ob/adm.pl>