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<p class="MsoNormal"><span style="color:windowtext">HI Mireille<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Re UCD type.<o:p></o:p></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.<o:p></o:p></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: <o:p></o:p></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.<o:p></o:p></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<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:windowtext"><primitiveType><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:windowtext"> <vodml-id>real</vodml-id><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:windowtext"> <name>real</name><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:windowtext"> <description>A real number (from R).</description><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:windowtext"></primitiveType><o:p></o:p></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)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">And the same is true for integer (N or Z), rational (Q), complex (C).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Cheers<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Gerard<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
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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 <dm-bounces@ivoa.net>
<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 <dm@ivoa.net><br>
<b>Subject:</b> Re: VODML base types : request for enhancement of the IVOA.1.0 template model<o:p></o:p></span></p>
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<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><o:p></o:p></p>
<p><o:p> </o:p></p>
<p><o:p> </o:p></p>
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<p>Dear DM, <o:p></o:p></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 . <o:p></o:p></p>
<p>it is in the PHOTDM specification , in the VODML translation from Modelio to XML. <o:p></o:p></p>
<p><a href="https://wiki.ivoa.net/internal/IVOA/PhotDM11RFC/Photv1_1_PR_20220520.html#UCD">https://wiki.ivoa.net/internal/IVOA/PhotDM11RFC/Photv1_1_PR_20220520.html#UCD</a><o:p></o:p></p>
<p>My understanding of IVOA BaseTypes, is that they should allow us to type the attributes of the classes exposed in the model. <o:p></o:p></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. <o:p></o:p></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 .<o:p></o:p></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. <o:p></o:p></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 . <o:p></o:p></p>
<p>I hope this helps , <o:p></o:p></p>
<p>Mireille<o:p></o:p></p>
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<p class="MsoNormal">Le 16/02/2026 à 11:23 AM, Markus Demleitner via dm a écrit :<o:p></o:p></p>
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<pre>Dear DM,<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>On Mon, Feb 16, 2026 at 09:39:55AM +0000, Paul Harrison via dm wrote:<o:p></o:p></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<o:p></o:p></pre>
<pre>it should conceptually by modelled with the SemanticConcept - but<o:p></o:p></pre>
<pre>it seems that the type of “topConcept” means that it cannot be used<o:p></o:p></pre>
<pre>to express the UCD string and there is possibly no conventional<o:p></o:p></pre>
<pre>value for the vocabularyURI for UCDs. (see<o:p></o:p></pre>
<pre><a href="https://github.com/ivoa/vo-dml/issues/19">https://github.com/ivoa/vo-dml/issues/19</a>)<o:p></o:p></pre>
</blockquote>
<pre>First off, VO-DML predates the current vocabulary spec, and therefore<o:p></o:p></pre>
<pre>limits itself to SKOS. That limitation should be lifted<o:p></o:p></pre>
<pre>independently of the UCD business. I'd be happy to review the<o:p></o:p></pre>
<pre>language on vocabulary usage for VO-DML 1.1, but I'd need some<o:p></o:p></pre>
<pre>poking. Perhaps we should even have an RDF serialisation for the<o:p></o:p></pre>
<pre>instances?<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>For the UCD question, however, all that iss not terribly helpful.<o:p></o:p></pre>
<pre>The reason is that UCDs have syntax. Modelling the UCD atoms as a<o:p></o:p></pre>
<pre>proper vocabulary is probably possible, and there's even a draft PR<o:p></o:p></pre>
<pre>for that <a href="https://github.com/ivoa-std/Vocabularies/pull/31"><https://github.com/ivoa-std/Vocabularies/pull/31></a>, but<o:p></o:p></pre>
<pre>you'd want ("compound") UCD words here, and RDF can't (really) do<o:p></o:p></pre>
<pre>that.<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>Me, I'm still skeptical that VO-DML should say a lot about UCDs<o:p></o:p></pre>
<pre>beyond mentioning that Quantity-s can be adorned with them in<o:p></o:p></pre>
<pre>sufficiently capable serialisations. But *if* there is a strong<o:p></o:p></pre>
<pre>reason to say "this must be a valid UCD", that'll need extra logic<o:p></o:p></pre>
<pre>beyond RDF.<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>Thanks,<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre> Markus<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>
<pre><o:p> </o:p></pre>
</blockquote>
<pre>-- <o:p></o:p></pre>
<pre>--<o:p></o:p></pre>
<pre>Mireille Louys, MCF (Assistant Professor)<o:p></o:p></pre>
<pre>Centre de données Astronomiques (CDS) Equipe Images, ICube<o:p></o:p></pre>
<pre>Observatoire de Strasbourg Telecom Physique Strasbourg<o:p></o:p></pre>
<pre>11, rue de l' Université 300, Bd Sebastien Brandt CS 10413<o:p></o:p></pre>
<pre>F-67000 Strasbourg F-67412 Illkirch Cedex<o:p></o:p></pre>
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