[om] About new XML encoding methods for OpenMath

[David Carlisle]

  Namely, Michael suggested to use instead of:
	<OMS name="in" cd="set1"/>
  to use, with a namespace declaration like
  xmlns:lset="http://www.openmath.org/cds/set1", the following
  	<lset:in/>

This has been suggested many times (since even before namespaces was a
REC, if I recall correctly), the main disadvantage is that given such an
approach one would essentially have to replace OMS by the ANY (xsd:any)
content model in any DTD (or schema) for openmath.

This means that

<OMA>
  <html:p>Some strange bit of xhtml
    <html:a  href="...">zzz</html:a>
 </html:p>
 <OMI>1</OMI>
</OMA>

would (assuming appropriate namespace declarations) validate against the
OM schema.

in otherwords there would be virtually no checks done at all by schema
validation, and more or less any random bits of well formed XML could be
included and it would still validate. "OM Validation" would have to be
specified as a layer above DTD/schema validation.

One could define special purpose schema which replaced xsd:any by
exactly the schema corresponding to the CDs that you want to support,
this would give a finer level of control than we have now, as then
schema validation would check that symbols used were in the CDs
specified, but it would require modifying the schema for each set of CDs
supported. 

Some days I think the benefits of this change outweigh the costs, and
some days I don't (I'm not sure which kind of day it is today)

David

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