VO-DML deployment

[Laurent MICHEL]

Markus,

The mechanism you are proposing would nice for a VO/service to deal with 
minir versions, but I'm asking to myself if is reasonable to ask the 
IVOA doc manager to manage .htaccess files?

Cheers
LM

Le 24/01/2017 à 10:18, Markus Demleitner a écrit :
> Dear DMers,
>
> In the context of the registration of data models, I spent a bit of
> time thinking about how VO-DML URIs should be managed so versioning
> "just works" while evolution remains naturally traceable.
>
> What I've come up with is included below. I think this could be a
> subsection before the registry topic proper; alternatively, it could
> be somewhere close to the start of the document. There, the DM URI is
> not formally introduced so far as far as I can see.  The first real
> indication that DMs have a URI indentifying them appears to be the
> Model.previousVersion, so it might be a good idea to make that a bit
> more explicit anyway.
>
> So, here's the prose I've drafted:
>
> ---------------------------- 8< ------------------------------
> X.Y Deploying VO-DML models
>
> To make VO-DML models usable, the model file needs to publicly
> available.  In order to ensure correct versioning semantics, the
> following constraints MUST be observed when publishing a VO-DML model:
>
> (a) the model URI MUST contain the major version of the model
>
> (b) the model URI MUST NOT contain the minor version of the model
>
> (c) resolving the model URI MUST, possibly after redirects, lead to
> the VO-DML for the latest minor version
>
> (d) resolving the model URI SHOULD result in an HTTP redirect to a
> URI that can be used to retrieve latest minor version of the VO-DML
> model; model providers SHOULD make sure that the URIs returned in this
> way remain stable for as long as possible so clients can, in principle,
> retrieve prior versions of the documents.
>
> For instance, the DM URI of the model defined in section Z.Z is
> http://ivoa.net/xml/ivoa/ivoa-v1.vo-dml.xml [TODO: or whatever -- make
> up a "best-practice" naming scheme as you want; I recommend a
> one-directory-per-DM scheme, though].  This will remain constant for all
> versions of the ivoa DM of the 1.0 series.
>
> When retrieving http://ivoa.net/xml/ivoa/ivoa-v1.vo-dml.xml, the server
> returns a document with an HTTP status code 303, redirecting (at the
> time of writing) to http://ivoa.net/xml/ivoa/ivoa-v1.0.vo-dml.xml.  The
> form of this second URL is not constrained by this specification, but
> obviously names containing the minor version explicitly are highly
> recommended.
>
> If the ivoa model is evolved, the redirect would end up at, say,
> http://ivoa.net/xml/ivoa/ivoa-v1.1.vo-dml.xml.  Clients that have for
> some reason cached the 1.0 URL could, however, keep on using it.
>
> Technical note: One way to implement this scheme using the popular HTTP
> server apache is to maintain an .htaccess file in the directory
> containing the various versions and follow a pattern like:
>
>   # sample .htaccess file for serving VO-DML
>   #
>   # This redirects the major version (the model URI) to the configured
>   # (should be latest) minor version XSD file
>
>   RewriteEngine On
>   RewriteBase /ivoa/
>
>   RewriteRule ^ivoa-v1.vo-dml.xml$ ivoa-v1.0.vo-dml.xml [R=303]
> ---------------------------- >8 ------------------------------
>
> The technical note may not be necessary.  But it shows how I've
> concocted an example deployment:
>
> On http://docs.g-vo.org/ivoa/ you could see all minor versions that
> there were (right now, there's just one).
>
> But on retrieving http://docs.g-vo.org/ivoa/ivoa-v1.vo-dml.xml,
> you'll get a redirect to the actual file, and that redirect would
> always point to the latest v1 file (compare curl and curl -L for that
> URL).
>
> With this scheme and the HTML-doc URL in the VO-DML model declaration
> (which would be another fixme), I think all aspects of a model would
> be discoverable based on the VO-DML URI in a way compatible with IVOA
> versioning rules.
>
> Opinions?
>
>          -- Markus
>

-- 
---- Laurent MICHEL              Tel  (33 0) 3 68 85 24 37
      Observatoire de Strasbourg  Fax  (33 0) 3 68 85 24 32
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