Version numbers on XMLschemata

Hi,

I've just been updating our copy of trhe schema for "VOResource 1.0" at Kevin's behest and I find this at the top:

<xs:schema targetNamespace="http://www.ivoa.net/xml/VOResource/v1.0"

           xmlns="http://www.w3.org/2001/XMLSchema"
           xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:vr="http://www.ivoa.net/xml/VOResource/v1.0"
           xmlns:vm="http://www.ivoa.net/xml/VOMetadata/v0.1"
           elementFormDefault="unqualified"
           attributeFormDefault="unqualified"
           version="1.02">

Can we _please_ not reuse XML namespaces with different content? If Registry-WG needs a v1.02 schema then _please_ put

<xs:schema targetNamespace="http://www.ivoa.net/xml/VOResource/v1.02"

           xmlns="http://www.w3.org/2001/XMLSchema"
           xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:vr="http://www.ivoa.net/xml/VOResource/v1.0"
           xmlns:vm="http://www.ivoa.net/xml/VOMetadata/v0.1"
           elementFormDefault="unqualified"
           attributeFormDefault="unqualified"
           version="1.02">

so that the namespace URI expresses the true version. In fact, I would not bother with the version attribute as it's too suspectible to misuse.

Changing a schema and keeping the same namespace is way too disruptive. If many instance documents get out using different interpretations of the namespace it's downright tragic. AstroGrid recently lost ~2 staff weeks of work because somebody once tweaked a schema and we didn't realize until months later when we started to depend on the changed details.

As Wil O'Mullane pointed out a while ago, vesion numbers are cheap and any time that we revise an exposed (= visible on web-site) artifact we ought to increment its version.

Cheers,
Guy

Guy Rixon 				        gtr-at-ast.cam.ac.uk
Institute of Astronomy   	                Tel: +44-1223-337542
Madingley Road, Cambridge, UK, CB3 0HA		Fax: +44-1223-337523