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<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 moz-do-not-send="true"
href="https://wiki.ivoa.net/internal/IVOA/PhotDM11RFC/Photv1_1_PR_20220520.html#UCD"
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>
<style type="text/css">p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 10.9px Helvetica; color: #063d8a}</style></p>
<p>
<style type="text/css">p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 10.9px Helvetica; col</style>So
the modeling at this level cannot take the precision into
account. </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 class="moz-cite-prefix">Le 16/02/2026 à 11:23 AM, Markus
Demleitner via dm a écrit :<br>
</div>
<blockquote type="cite"
cite="mid:s2ga7ht4p5l6xb7c3ybcxvmefzfubm7cdakqcas4yllhltn6nb@6yqmjkf5y2ur">
<pre wrap="" class="moz-quote-pre">Dear DM,
On Mon, Feb 16, 2026 at 09:39:55AM +0000, Paul Harrison via dm wrote:
</pre>
<blockquote type="cite">
<pre wrap="" class="moz-quote-pre">I think that if a particular model element have a constant UCD then
it should conceptually by modelled with the SemanticConcept - but
it seems that the type of “topConcept” means that it cannot be used
to express the UCD string and there is possibly no conventional
value for the vocabularyURI for UCDs. (see
<a class="moz-txt-link-freetext"
href="https://github.com/ivoa/vo-dml/issues/19">https://github.com/ivoa/vo-dml/issues/19</a>)
</pre>
</blockquote>
<pre wrap="" class="moz-quote-pre">First off, VO-DML predates the current vocabulary spec, and therefore
limits itself to SKOS. That limitation should be lifted
independently of the UCD business. I'd be happy to review the
language on vocabulary usage for VO-DML 1.1, but I'd need some
poking. Perhaps we should even have an RDF serialisation for the
instances?
For the UCD question, however, all that iss not terribly helpful.
The reason is that UCDs have syntax. Modelling the UCD atoms as a
proper vocabulary is probably possible, and there's even a draft PR
for that <a class="moz-txt-link-rfc2396E"
href="https://github.com/ivoa-std/Vocabularies/pull/31"><https://github.com/ivoa-std/Vocabularies/pull/31></a>, but
you'd want ("compound") UCD words here, and RDF can't (really) do
that.
Me, I'm still skeptical that VO-DML should say a lot about UCDs
beyond mentioning that Quantity-s can be adorned with them in
sufficiently capable serialisations. But *if* there is a strong
reason to say "this must be a valid UCD", that'll need extra logic
beyond RDF.
Thanks,
Markus
</pre>
</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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