Doubts with the facility name term

[Stéphane Erard]

Hello 

As you know, in EPNCore we use a simple system to facilitate data search:

Instrument_host_name : is an observatory, spacecraft, or facility ( = lab) - by observatory here, we really mean: telescope
Instrument_name : is an instrument, either spatial, accommodated on the telescope, or in the lab

Since EPNCore parameters support list of values, indications broader than a single telescope (observatory site) can also be included here.

We can also provide a finer structure with:
detector_name to specify a single detector in complex instruments, typically a channel in a space borne instrument. 
opt_elem for optional optical elements (grating, etc)

E.g.:
I find HST data with Instrument_host_name  LIKE ‘%HST%’ 
	or ivo_hashlist_has(Instrument_host_name, ‘HST') = 1

And I’ll use the same query to look for data from Paranal or ESO (with little chance of success I must say).
- Same for Rosetta Orbiter and Rosetta - they would both share the same parameter if provided
But I see little reasons to search for ESO (or ESA), at least for users with EPNCore (although it makes sense when querying the registry, but I expect the data origin to be specified there).

There may be a missing parameter in EPNcore, but we all know that describing a hierarchy of things with 10 keywords is always counterproductive — the user never knows where the search value has to be located, and data providers got it wrong half the time (e.g., mineral descriptions in lab databases are living nightmares - here we decided to put everything in a single parameter with no special order).


I must add that what makes the system work is really to use limited lists of possible values, simple names with no fancy variations (lesson learnt from PDS3). 

Hope this helps,
Stéphane


> Le 9 févr. 2022 à 11:13, Markus Demleitner <msdemlei at ari.uni-heidelberg.de> a écrit :
> 
> Dear Semantics folks,
> 
> On Thu, Feb 03, 2022 at 02:20:46PM +0100, Tamara Civera wrote:
>> I am writing to this group, because trying to unify the facility name in the
>> different VO services offered by my observatory (SIAP, Obscore,...) the
>> following doubt has arisen: *Should the facility name describe only the
>> facility or observatory, the telescope or both?*
>> 
>> According to the different VO protocols documentation:
>> 
>> Obscore: "B7.1 The Facility class codes information about the observatory or
>> facility used to collect the data."
>> 
>> Obscore: "C.3 <FIELDname="facility_name"datatype="char"ucd="meta.id;instr.tel"utype="obscore:Provenance.ObsConfig.Facility.name"xtype="adql:VARCHAR"arraysize="128*"><DESCRIPTION>telescope
>> name</DESCRIPTION></FIELD>"
>> 
>> SIAP 2.0: "2.1.12 The FACILITY parameter is a string-valued parameter that
>> specifies the name of the facility (usually telescope) where the data was
>> acquired. The value is compared with the facility_name from the ObsCore [7]
>> data model"
>> 
>> VoDataService: "3.1.1 The observatory or facility used to collect the data
>> contained or managed by this resource."
> 
> Tamara raises a very valid point here, one that I've often briefly
> puzzled over only to just move on and ignore the problem.  
> 
> I think that if we want these fields to be reliably usable, we ought
> to make up our minds (and then perhaps clarify the various standards
> using errata).
> 
> As usual, I'd suggest we start by working out what functionality
> should be enabled by the feature; historically: what motivated the
> addition of facility_name in Obscore and VODataService (and,
> conversely, what made the SSAP authors to only have instrument).  If
> anyone reading this remembers, please chime in.
> 
> If you ask me, I'd say the main conceivable use case would be queries
> -- whether for data sets as in obscore or for data collections in the
> Registry -- of the type "Give me data from the HST" (which then would
> include any sort of detector; my impression is that there's
> relatively wide consensus that that would be in the instrument
> field).  This, however, gets more complicated when there are multiple
> telescopes at one site (facility?).  Let's take ESO's La Silla as an
> example, where (I think) there are about a dozen individual
> telescopes (or telescope-like... things, to avoid the term
> "instrument" that we've just used for detectors).  
> 
> Which reminds me: The FITS standard
> <https://heasarc.gsfc.nasa.gov/docs/fcg/standard_dict.html> has the
> TELESCOP keyword for pretty much this -- does anyone remember why we
> didn't just take that over?  Was it because we wanted to cover
> devices that don't feel like telescopes at all like, perhaps the GBM
> aboard Fermi, the Icecube-like neutrino detectors, or LIGO/Virgo?)
> 
> Resuming the La Silla example, I'd venture giving the concrete
> telescope ("ESO 3.6 m", "NTT", ...) will more likely be useful for
> actual searches than the generic "La Silla", as the individual
> telescopes have so different properties that it seems unlikely to me
> that a scientifically relevant question could use them in grouped
> form.
> 
> Against that could be a situation in which someone remembers that
> some data set they've seen, say, at a conference, was "taken
> somewhere at La Silla".  That, for one, seems a less likely scenario
> to me; also, if and when we have usable
> dictionary/vocabulary/taxonomy of "instruments" (now in the general
> meaning), it would be fairly straightforward to translate such
> a query into a query based on the individual telescope names.
> 
> After this, I'm frankly tempted to try and clearly state that
> "facility" should be, to first order, the telescope, and we ought to
> explictly link it to FITS' TELESCOP.  Which, by the way, is defined
> as
> 
>  The value field shall contain a character string identifying the
>  telescope used to acquire the data associated with the header.
> 
> I can't say I'm too happy with using "telescope" in this definition
> as our "collectors" are becoming more diverse and exotic.  In a way,
> I'd be tempted to try and separate facility_name and instrument into
> "device that collects/concentrates messenger particles" and "device
> that detects messenger particles".  For Icecube-like devices, that
> would happen to coincide, but that's perhaps not problematic.
> 
> Well, having said all this: I suspect there's a bit of prior art on
> this.  If you have pointers, by all means share them.  And would
> anyone volunteer to run a discussion on this problem at the Interop?
> 
>            -- Markus