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<div class="moz-cite-prefix">Le 17/10/2023 à 10:38, Gregory MANTELET
a écrit :<br>
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<blockquote type="cite"
cite="mid:8bec204f-4b6f-487f-a26f-e5bf3b13513f@astro.unistra.fr">
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Dear DAL members,<br>
<br>
Here is an announcement for an exceptional DAL running meeting,
probably the last one before the May Interop.<br>
<br>
The goal is to speak about the last on-going issues with the
Datalink RFC (mainly, PullRequest <a
href="https://github.com/ivoa-std/DataLink/pull/110"
moz-do-not-send="true">#110</a>). Right now, the central
question is how to convey the content type of a link document so
that it can be easily recognized and used by clients.<br>
<br>
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<p
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face="monospace">Topic: DAL Running Meeting #17 - Datalink</font></p>
<p
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face="monospace">Time: Oct 18, 2023 08:00 PM Universal Time UTC</font></p>
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<p
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<p
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face="monospace"><a
href="https://cnrs.zoom.us/j/95304890218?pwd=cFpTM3JZSEZJUktoWUlaM3MzaTl6QT09"
class="moz-txt-link-freetext" moz-do-not-send="true">https://cnrs.zoom.us/j/95304890218?pwd=cFpTM3JZSEZJUktoWUlaM3MzaTl6QT09</a></font></p>
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<p
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face="monospace">Meeting ID: 953 0489 0218</font></p>
<p
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face="monospace">Passcode: 63a2d5</font></p>
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<p
style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;">Sorry for the last minute organization. We hope that most of interested people can attend anyway. If you can not, but have anyway
something to say, do not hesitate to send your comments to James and I so that we can share them with the participants during the meeting. We will also write notes that we will share with all of you after the meeting.</p>
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<p
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<p
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<p>Dear Dalers,</p>
<p>The topic to be discussed is the following (see github PR <a class="moz-txt-link-freetext" href="https://github.com/ivoa-std/DataLink/pull/110">https://github.com/ivoa-std/DataLink/pull/110</a>) :</p>
<p>Should we remove section 3.1.1 or at least change the proposal inside ? The subsection in the PR is different from the one in the current draft. See attached pdf for the last proposal.</p>
<p>The issue it is supposed to solve (according to me at least) is the following :</p>
<p> How do we recognize or build that an URL in VOTable document is pointing to a DataLink {links} endpoint or document when we are not in the ObsCore context ?</p>
<p> <i>This issue appeared as early as 2017 (1.5 year after the DataLink1.0 release) when people started to use DataLink in other contexts (for example in catalog of sources) :</i></p>
<p><i> See for example Shanghai , Santiago and Victoria presentations :</i></p>
<p><i><a class="moz-txt-link-freetext" href="https://wiki.ivoa.net/internal/IVOA/InterOpMay2017-DAL/DataLinkDatasetAccessEvolution.pdf">https://wiki.ivoa.net/internal/IVOA/InterOpMay2017-DAL/DataLinkDatasetAccessEvolution.pdf</a>
</i></p>
<p><i><a class="moz-txt-link-freetext" href="https://wiki.ivoa.net/internal/IVOA/InterOpOct2017DAL/DataLinkSolution.pdf">https://wiki.ivoa.net/internal/IVOA/InterOpOct2017DAL/DataLinkSolution.pdf</a></i></p>
<p><i><a class="moz-txt-link-freetext" href="https://wiki.ivoa.net/internal/IVOA/InterOpMayy2018DAL/dlink-victoria.pdf">https://wiki.ivoa.net/internal/IVOA/InterOpMayy2018DAL/dlink-victoria.pdf</a></i></p>
<p><i><a class="moz-txt-link-freetext" href="https://wiki.ivoa.net/internal/IVOA/InterOpMayy2018DAL/DAL-Feedback.pdf">https://wiki.ivoa.net/internal/IVOA/InterOpMayy2018DAL/DAL-Feedback.pdf</a></i></p>
<p><i>In regretted Carlos (RIP) presentation you will find examples of DataLink in SCS services</i></p>
<p><i>I summarized the ideas in one section of an IVOA note in 2018 : <a class="moz-txt-link-freetext" href="https://www.ivoa.net/documents/Notes/RecentDALProtocolsFeedback/20180722/index.html">https://www.ivoa.net/documents/Notes/RecentDALProtocolsFeedback/20180722/index.html</a></i></p>
<p><i>Solutions were also discussed in College Park and Paris meetings as well as on github and some DAL running meetings since then </i></p>
<p><i><a class="moz-txt-link-freetext" href="https://wiki.ivoa.net/twiki/bin/view/IVOA/DataLink-1_0-Next">https://wiki.ivoa.net/twiki/bin/view/IVOA/DataLink-1_0-Next</a> (Paris splinter)</i></p>
<p><i><a class="moz-txt-link-freetext" href="https://wiki.ivoa.net/internal/IVOA/InterOpNov2018DAL/DataLink-next.pdf">https://wiki.ivoa.net/internal/IVOA/InterOpNov2018DAL/DataLink-next.pdf</a></i></p>
<p><i><a class="moz-txt-link-freetext" href="https://github.com/ivoa-std/DataLink/issues/29">https://github.com/ivoa-std/DataLink/issues/29</a> (and related PRs)</i></p>
<p><i>Some text was already written in various sections ans appendices of the first version of DataLink 1.1 internal draft : <a class="moz-txt-link-freetext" href="https://wiki.ivoa.net/internal/IVOA/DataLink-1_0-Next/DataLink.pdf">https://wiki.ivoa.net/internal/IVOA/DataLink-1_0-Next/DataLink.pdf</a></i></p>
<p><i>
</i></p>
<p>How can we recognize these URL or DatLink endpoint ?</p>
<p>- If the URL can be built from the content of a column considered as the admitted ID value in the DataLink URL then we can use a service descriptor</p>
<p>- If data providers provide a full URL in one of the columns , a LINK element can be included in the corresponding FIELD element with content_type = "application/x-votable+xml;content=datalink"
</p>
<p><i> </i> ---> The argument against that is that it is actually not specific to DataLink and could be devlopped in VOTable 1.5 or later for all kind of content_types.<i> </i></p>
<p>I am not against doing that but I think that the mechanism shoud be explained in DAataLInk 1.1 anyway in the mean time. If not in main text in appendix</p>
<p>- If data providers provide an URL pointing sometimes to DataLink {links} sometime to a real dataset or document then we should use a second column to provide the format with a ref to the URL column.</p>
<p> The Access.reference and Access.format should be set on the two FIELDS as defining the role of these two FIELDS unambiguously.</p>
<p> ---> The argument against that is that this could enter in conflict other datamodel utypes for the same FIELDS</p>
<p>By looking to current list of utypes in datamodels which provide some I don't think such a conflict can happen</p>
<p>(and anyway we still have the GROUP + FIELDREf to duplicate utypes on the FIELDS).</p>
<p>Actually the Access class in Obscore with its three attributes Reference, format and estimated_size is common with SSA and is implicitely there in {links} response itself (FIELDS access_url, content_type and content_length)</p>
<p>Access is actually a generic class hich can be imported in several datalodels</p>
<p>Cheers</p>
<p>François
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