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

[Mireille Louys]

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://github.com/ivoa/HighEnergyObsCoreExt/issues/48>

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://github.com/ivoa/HighEnergyObsCoreExt/issues/39#issuecomment-4208293821

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

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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