RelaxNG and versioning - example

Hello David,

On the tag call I suggested an example to discuss wrt RelaxNG and
versioning. You asked for an email about that, to remind you:

a) version n has an empty element foo

version n+1 has an attribute bar on element foo; if bar="baz" then the
content model is not empty but has a child toto.

b) version n has an attribute blah

version n+1 can either have an attribute blah or a child blah, but not
both.

RelaxNG can express these sorts of co-constraint, as Norm confirmed on
the call.

(as a practical example, moving from a title attribute to having a title
child, that sort of thing)

-- 
 Chris Lilley                    mailto:chris@w3.org
 Chair, W3C SVG Working Group
 Member, W3C Technical Architecture Group