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<p>Hi Gerard , </p>
<p>thanks for your answer . </p>
<p>Real type :</p>
<p>yes I used the abstract 'ivoa:real ', but In my use-case , I
would like to state "in the model" that it should be a double
precision . <br>
Currently the IVOA:Basetype model cannot tell this. <br>
or did I miss anything? </p>
<p>ucd as <semantic_concept>:</p>
<p>the Semantics group is working on a representation of the UCD
terms as a Vocabulary . </p>
<p>But a Ucd contains a concatenation of ucd terms , for which no
uri are defined yet, like in a fully defined vocabulary. </p>
<p>so the best option , in the PhotDM use case, was to derive ucd
from ivoa:string , and define it as a concatenation of members of
the UCDList specification , which is/will be a vocabulary . </p>
<p>Cheers, Mireille</p>
<div class="moz-cite-prefix">Le 16/02/2026 à 7:37 PM, Gerard Lemson
a écrit :<br>
</div>
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<p class="MsoNormal"><span style="color:windowtext">HI Mireille</span></p>
<p class="MsoNormal"><span style="color:windowtext">Re UCD type.</span></p>
<p class="MsoNormal"><span style="color:windowtext">I think this
does not change the comment in my previous email. Thie is
precisely what the <<semanticconcept>>
stereotype is for.</span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Re zero
point: </span></p>
<p class="MsoNormal"><span style="color:windowtext">The
ivoa:real IS NOT a 32 bit float. It represents the
mathematical concept of a real number.</span></p>
<p class="MsoNormal"><span style="color:windowtext">Is not very
explicit in the data model, but that is what is intended by
the “from R” in</span></p>
<p class="MsoNormal"><span
style="font-family:"Courier New";color:windowtext"><primitiveType></span></p>
<p class="MsoNormal"><span
style="font-family:"Courier New";color:windowtext">
<vodml-id>real</vodml-id></span></p>
<p class="MsoNormal"><span
style="font-family:"Courier New";color:windowtext">
<name>real</name></span></p>
<p class="MsoNormal"><span
style="font-family:"Courier New";color:windowtext">
<description>A real number (from
R).</description></span></p>
<p class="MsoNormal"><span
style="font-family:"Courier New";color:windowtext"></primitiveType></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Again, it is
a serialization choice how to represent these (16,32,64 bit
floats for example, or decimal numbers)</span></p>
<p class="MsoNormal"><span style="color:windowtext">And the same
is true for integer (N or Z), rational (Q), complex (C).</span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Cheers</span></p>
<p class="MsoNormal"><span style="color:windowtext">Gerard</span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<div>
<div
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<p class="MsoNormal"><b><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext">From:</span></b><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext">
dm <a class="moz-txt-link-rfc2396E" href="mailto:dm-bounces@ivoa.net"><dm-bounces@ivoa.net></a>
<b>On Behalf Of </b>Mireille Louys via dm<br>
<b>Sent:</b> Monday, February 16, 2026 1:13 PM<br>
<b>To:</b> Data Models mailing list <a class="moz-txt-link-rfc2396E" href="mailto:dm@ivoa.net"><dm@ivoa.net></a><br>
<b>Subject:</b> Re: VODML base types : request for
enhancement of the IVOA.1.0 template model</span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p><b><br>
</b><strong><span style="color:white;background:red"> External
Email - Use Caution </span></strong></p>
<p><o:p> </o:p></p>
<p><o:p> </o:p></p>
<div>
<p>Dear DM, </p>
<p>In order to help to stabilize on a use-case , here is an
example where I needed to derive types from the
IVOA:Basetypes . </p>
<p>it is in the PHOTDM specification , in the VODML
translation from Modelio to XML. </p>
<p><a
href="https://wiki.ivoa.net/internal/IVOA/PhotDM11RFC/Photv1_1_PR_20220520.html#UCD"
moz-do-not-send="true" class="moz-txt-link-freetext">https://wiki.ivoa.net/internal/IVOA/PhotDM11RFC/Photv1_1_PR_20220520.html#UCD</a></p>
<p>My understanding of IVOA BaseTypes, is that they should
allow us to type the attributes of the classes exposed in
the model. </p>
<p>I have derived the type UCD in PhotDM as an ivoa:string ,
that can be interpreted as an expression defined in the
UCDList specification. </p>
<p>For the ZeroPoint class, I needed attributes expressed in
double precision like ZeroPoint.flux.value,
and ZeroPoint.referenceMagnitude.value but IVOA:Basetypes
offers only ivoa:real .</p>
<p>So I wish the IVOA BaseTypes could be extended to contain
the basic types that are used , in VOTable serialisation and
XML basic types for instance. </p>
<p>In this use-case , I undertand I stick to the initial XML
oriented VO formats and that documents serialized in JSON
would need a mapping . </p>
<p>I hope this helps , </p>
<p>Mireille</p>
<div>
<p class="MsoNormal">Le 16/02/2026 à 11:23 AM, Markus
Demleitner via dm a écrit :</p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<pre>Dear DM,</pre>
<pre><o:p> </o:p></pre>
<pre>On Mon, Feb 16, 2026 at 09:39:55AM +0000, Paul Harrison via dm wrote:</pre>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<pre>I think that if a particular model element have a constant UCD then</pre>
<pre>it should conceptually by modelled with the SemanticConcept - but</pre>
<pre>it seems that the type of “topConcept” means that it cannot be used</pre>
<pre>to express the UCD string and there is possibly no conventional</pre>
<pre>value for the vocabularyURI for UCDs. (see</pre>
<pre><a href="https://github.com/ivoa/vo-dml/issues/19"
moz-do-not-send="true" class="moz-txt-link-freetext">https://github.com/ivoa/vo-dml/issues/19</a>)</pre>
</blockquote>
<pre>First off, VO-DML predates the current vocabulary spec, and therefore</pre>
<pre>limits itself to SKOS. That limitation should be lifted</pre>
<pre>independently of the UCD business. I'd be happy to review the</pre>
<pre>language on vocabulary usage for VO-DML 1.1, but I'd need some</pre>
<pre>poking. Perhaps we should even have an RDF serialisation for the</pre>
<pre>instances?</pre>
<pre><o:p> </o:p></pre>
<pre>For the UCD question, however, all that iss not terribly helpful.</pre>
<pre>The reason is that UCDs have syntax. Modelling the UCD atoms as a</pre>
<pre>proper vocabulary is probably possible, and there's even a draft PR</pre>
<pre>for that <a
href="https://github.com/ivoa-std/Vocabularies/pull/31"
moz-do-not-send="true"><https://github.com/ivoa-std/Vocabularies/pull/31></a>, but</pre>
<pre>you'd want ("compound") UCD words here, and RDF can't (really) do</pre>
<pre>that.</pre>
<pre><o:p> </o:p></pre>
<pre>Me, I'm still skeptical that VO-DML should say a lot about UCDs</pre>
<pre>beyond mentioning that Quantity-s can be adorned with them in</pre>
<pre>sufficiently capable serialisations. But *if* there is a strong</pre>
<pre>reason to say "this must be a valid UCD", that'll need extra logic</pre>
<pre>beyond RDF.</pre>
<pre><o:p> </o:p></pre>
<pre>Thanks,</pre>
<pre><o:p> </o:p></pre>
<pre> Markus</pre>
<pre><o:p> </o:p></pre>
<pre><o:p> </o:p></pre>
<pre><o:p> </o:p></pre>
<pre><o:p> </o:p></pre>
<pre><o:p> </o:p></pre>
</blockquote>
<pre>-- </pre>
<pre>--</pre>
<pre>Mireille Louys, MCF (Assistant Professor)</pre>
<pre>Centre de données Astronomiques (CDS) Equipe Images, ICube</pre>
<pre>Observatoire de Strasbourg Telecom Physique Strasbourg</pre>
<pre>11, rue de l' Université 300, Bd Sebastien Brandt CS 10413</pre>
<pre>F-67000 Strasbourg F-67412 Illkirch Cedex</pre>
</div>
</div>
</blockquote>
<pre class="moz-signature" cols="72">--
--
Mireille Louys, MCF (Assistant Professor)
Centre de données Astronomiques (CDS) Equipe Images, ICube
Observatoire de Strasbourg Telecom Physique Strasbourg
11, rue de l' Université 300, Bd Sebastien Brandt CS 10413
F-67000 Strasbourg F-67412 Illkirch Cedex</pre>
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