[Heig] UCD discussion : summary of the recent discussion through the github repo ivoa/HighEnergyObscoreExtension

Thu Apr 16 20:04:37 CEST 2026

Dear HEIG,

As a follow-up, the latest draft HEIG proposals for updates to the UCD vocabulary are listed in section 5.3 of the draft HEIG ObsCore Extension document (dated 2025-11-12), which can be found on GitHub at https://github.com/ivoa/HighEnergyObsCoreExt

Some of the preliminary proposals (e.g., phys.flux etc) were updated in this version of the document.

Thanks,
—Ian

> On Apr 16, 2026, at 13:05, Mireille Louys via heig <heig at ivoa.net> wrote:
> 
> 
> 
> Hello Heig members, 
> 
> In order to prepare the discussion about UCDs tomorrow, 
> here is a short summary of were we stand in the UCD proposal and the discussions with the Semantics WG: 
> 
> Reminder : 
> 
> We must keep in mind that the UCD vocabulary helps to categorize the quantities or labels or information present in a table column. 
> It is not a data model class attribute , which is designed specificaly for the domain it is used for . 
> 
> UCDs are used in tables stored as VOTable, either in data tables , like in the Vizier catalog tables for instance , 
> or in metadata tables like in TAP query responses ( as in ObsTAP) or Cone search response, for instance. 
> 
> For the various UCDs discussed in this group , they deal with : 
> 
> event
> For an event_list data set, expressed as a table , column names describe the kind of quantities recorded for an event and can be tagged by a UCD . 
> The event_list table has one event per row , with all quantities values in the various columns. 
> 
> In order to designate an high energy event, we have proposed  obs.event together with Bruno  and the semantics chairs in december 2025.
> See here the corresponding issue : https://github.com/ivoa/HighEnergyObsCoreExt/issues/48
> S     obs.event     Related to a signal messenger detection (photon or particle) <https://www.google.com/url?q=https://github.com/ivoa/HighEnergyObsCoreExt/issues/48&source=gmail-imap&ust=1776963930000000&usg=AOvVaw1kLB91UZl8MDWiAcyIu2ex>
> It does not define what an event is ( this is up to the data model) but it says how to relate a quantity to an event .
> 
> then columns related to an event can be tagged with 
> 
> column name  |  ucd 
> event_id             meta.id;obs.event
> event_type         meta.code.class;obs.event
> event_grade       meta.code.class;obs.event
> 
> pha
> Thanks to Ian for the example about PHA quantities related to an event:
> see https://github.com/ivoa/HighEnergyObsCoreExt/issues/39 <https://www.google.com/url?q=https://github.com/ivoa/HighEnergyObsCoreExt/issues/39&source=gmail-imap&ust=1776963930000000&usg=AOvVaw3_9C-FlhVraF-GhS0YkJf6> 
> https://github.com/ivoa/HighEnergyObsCoreExt/issues/39#issuecomment-4208293821 <https://www.google.com/url?q=https://github.com/ivoa/HighEnergyObsCoreExt/issues/39%23issuecomment-4208293821&source=gmail-imap&ust=1776963930000000&usg=AOvVaw08E5hDjT0J3NAzaVNTPO6H>
> I have tried to tag the UCDs corresponding to the various columns 
> using instr.pulse  suggested above in the issue thread. 
> 
> Most of the quantities can be UCD anotated as shown in this issue.
> 
> A problem remains for :
> 
> pi    pulse invariant amplitude, calculated from energy (and therefore pha), this value is needed to compute the rmf
> 
> Can we clarify this quantity? 
> 
> phys.flux/ phys.flux.density   work in progress (B. Khelifi)
> to be discussed further 
> phys.particle  a VEP has been proposed at 
> https://voparis-gitlab.obspm.fr/vespa/ivoa-standards/semantics/vep-ucd/-/blob/master/VEP-UCD-26-particle_types.txt <https://www.google.com/url?q=https://voparis-gitlab.obspm.fr/vespa/ivoa-standards/semantics/vep-ucd/-/blob/master/VEP-UCD-26-particle_types.txt&source=gmail-imap&ust=1776963930000000&usg=AOvVaw04HouvV29NivgznISOCDXl>Cheers, Mireille
> 
> 
> 
> -- 
> --
> 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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—

Dr. Ian Evans
Astrophysicist
Chandra X-ray Center
Center for Astrophysics | Harvard & Smithsonian

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