VODML base types : request for enhancement of the IVOA.1.0 template model

[Mireille Louys]

Dear DM,

In order to help to stabilize on a use-case , here is an example where I 
needed to derive types from the IVOA:Basetypes .

it is in the PHOTDM specification , in the VODML translation from 
Modelio to XML.

https://wiki.ivoa.net/internal/IVOA/PhotDM11RFC/Photv1_1_PR_20220520.html#UCD

My understanding of IVOA BaseTypes, is that they should allow us to type 
the attributes of the classes exposed in the model.

I have derived the type UCD in PhotDM as an ivoa:string , that can be 
interpreted as an expression defined in the UCDList specification.

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 .

So the modeling at this level cannot take the precision into account.

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.

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 .

I hope this helps ,

Mireille

Le 16/02/2026 à 11:23 AM, Markus Demleitner via dm a écrit :
> Dear DM,
>
> On Mon, Feb 16, 2026 at 09:39:55AM +0000, Paul Harrison via dm wrote:
>> 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
>> https://github.com/ivoa/vo-dml/issues/19)
> 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<https://github.com/ivoa-std/Vocabularies/pull/31>, 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
>
>
>
>
>
-- 
--
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
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