VO-DML uri element

[Gerard Lemson]

Hi Paul


On Tue, Jun 13, 2017 at 3:59 AM, Paul Harrison <
paul.harrison at manchester.ac.uk> wrote:

> Hi,
>
> I notice that a recent change to the VO-DML schema introduces a <uri>
> element which is supposed to define a URI at which the data model can be
> found - in my opinion this is not a good idea. I understand the desire to
> have a standard place to look data models up, but this is better defined
> outside the data model file itself. There is a certain tautology in the
> fact that if you have possession of the data model instance file then you
> have obtained it from a URI somewhere, so you already know that URI -
> conversely if you do not have the data model file then you do not know
> where to look it up without external rules if that URI is allowed to be
> arbitrary.
>
> Each data model already has a “namespace” which is the <name> element and
> just having a rule such as the models being available at
>
> http://www.ivoa.net/dm/name
>
> would suffice for all “standard” models - though there could be a more
> arbitrary mapping mechanism set up between namespace and model URL such as
> is done with XML.
>
>
Indeed this mechanism is what we're trying to follow. If the description in
the document (still on volute, soon to be moved to IVOA doc library) is not
clear enough though we need to improve the text.

The URI attribute is *not* intended to be location of the document, but to
be dereferenced to the latest minor version. Different minor versions will
have same URI, but different "version" attribute. So together , uri+version
are a unique identifier of the actual version, uri only of the major
version.

But I expect Markus can explain this better.

Cheers



Gerard



> Regards,
>         Paul.
>
>
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