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---++ XML Schema Versioning Policies: Endorsed Note - Request for TCG Comments and Approvals

Document Link: [[http://www.ivoa.net/documents/Notes/XMLVers/index.html][XML Schema Versioning Policies]]

---++ Comments from TCG members

WG chairs or vice chairs must read the Note, provide comments if any and formally indicate if they approve or do not approve of the Note. IG chairs or vice chairs are also encouraged to do the same, although their inputs are not compulsory.

---+++ TCG Chair & Vice Chair ( _Matthew Graham, Pat Dowler_ )

---+++ Applications Working Group ( _Pierre Fernique, Tom Donaldson_ )

---+++ Data Access Layer Working Group ( _François Bonnarel, Marco Molinaro_ )

---+++ Data Model Working Group ( _Mark Cresitello-Dittmar, Laurent Michel_ )

---+++ Grid & Web Services Working Group ( _Brian Major, Giuliano Taffoni_ )

---+++ Registry Working Group ( _Markus Demleitner, Theresa Dower_ )

(1) I'm not sure I like the language of

<blockquote>We can use the observation that simply removing the namespace definition from both instances would make the instances both textually the same and equivalent in the strict XML sense to inform the class of changes can be to the schema definition without necessarily needing to change the namespace, and how a client should treat such changes.</blockquote>

(introduction to section 2). I have an uncanny feeling that I don't understand what this is intended to mean. Also, it may be confusing in this context, even more so since

<verbatim>
  <doc xmlns="http://example.com/ns"/>
</verbatim>

and

<verbatim>
  <ns:doc xmlns:ns="http://example.com/ns"/>
</verbatim>

indeed are equivalent.

Plus, I think we should not even suggest removing the namespace declarations might be a good idea under any circumstances, as doing this is certain to cause major interoperability problems as soon as the resulting tree is serialised again. I'd vote to remove the entire introductory paragraph to section 2.

(2) In

<blockquote>Hence, in service responses, root elements must have a \xmlel{version} attribute exactly giving the value of the corresponding XSD file's \xmlel{version} attribute.</blockquote>

I'm doubtful of the must. Ok, it is limited to "service responses", but that's a term not clearly defined. In VOResource, for instance, I don't think vr:Resource/@version is terribly useful; worse, the root element of actual responses of OAI-PMH-services is a container element we don't even control. And VOResource doesn't have global elements in the first place. So, I'm much rather have language like:

<blockquote>For such applications, protocols should place \xmlel{version} attributes, typically on the root element(s) of the schema. Their values exactly correspond to the value of the \xmlel{version} attribute on the \xmlel{xs:schema} (i.e., root) element of the XML schema file against which a given piece of software was implemented.</blockquote>

And then we could strike the sentence "When the discovery of ... may be left out" further down.

(3) I think the global exposition would profit if we first discuss xs.schema/@version (current sect 2.2.2) and only then talk about @version in instance documents -- since the schema file is the source of the version string, that seems a bit more logical.

(4) While I personally am a big fan of the plural "schemata", I feel obliged to mention that if we wrote "schema files" instead, we'd probably be subscribing to less controversial terminology.

None of the above points is really serious, though, so regardless of how they are eventually decided, I approve of this document.

---+++ Semantics Working Group ( _Mireille Louys, Alberto Accomazzi_ )

---+++ Education Interest Group ( _Massimo Ramella, Sudhanshu Barway_ )

---+++ Time Domain Interest Group ( _John Swinbank, Mike Fitzpatrick_ )

---+++ Data Curation & Preservation Interest Group ( _Françoise Genova_ )

---+++ Operations Interest Group ( _Tom !McGlynn, Mark Taylor_ )

---+++ Knowledge Discovery in Databases Interest Group ( _George Djorgovski_ )

---+++ Theory Interest Group ( _Franck Le Petit, Carlos Rodrigo_ )<br /><br /> ---+++ Standards and Processes Committee ( _Françoise Genova_)

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Topic revision: r2 - 2016-04-25 - MarkusDemleitner
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