Show Stopper 2 Problem Statement

[Martin Bryan <mtbryan@sgml.u-net.com>]

No mechnaism is defined within the ebXML Constraint language to record
relationships between elements. It is not, therefore, possible to state that
element X may only occur if element Y is present (unless they are siblings
and two choices of model are defined) or that element X must occur if
element Y contains value Z.

I had worked out a way that this could be done using W3C XML Schemas,  but
the decision of the group that the constraint language must be capable of
generating any type of XML validation mechanism, including DTDs, Schematron,
etc, makes it impossible to come up with any mechanism for expressing such
relationships that can be consistently applied.

Martin Bryan
The SGML Centre