same and synonym Re: IAU thesaurus in RDF (an update)

[Frederic V. Hessman]

On 8 Oct 2007, at 7:09 pm, Bernard Vatant wrote:

> Ed
>> Is infrared_radiation synonymous with infrared_emission?  I don't  
>> see a way for SKOS to say SameAs.  How does one say iau:stars  
>> sameas cds:stars?
> This is a complex issue - and to say the truth my favourite one -  
> with different aspects. So I have to bite here :-)
>
> 1. Synonymy is dealt with in SKOS as in standard thesaurus  
> practice. Defining a controlled vocabulary is all about defining a  
> sort of closed linguistic world where the "unique name assumption"  
> holds, which means distinct concepts bear distinct labels, and  
> every concept has a single (preferred) label (in a given language).  
> So if you have synonymous like "infrared emission" and "infrared  
> radiation" (supposing they are actually synonymous, which IMHO  
> seems questionable, but this is not the point), the controlled  
> vocabulary authority, based on what is considered as the best  
> naming practice. Suppose you recommend "infrared radiation" over  
> "infrared emission", you will have in classical thesaurus :
>
> /Infrared Emission
>    /USE   Infrared Radiation/
> /
> Infrared Radiation
>    UF /Infrared Emission
> /
> In SKOS, the same semantics is achieved using skos:prefLabel and  
> skos:altLabel.
>
> iau:_123456  skos:prefLabel   'infrared radiation' @en
> iau:_123456  skos:altLabel   'infrared emission' @en
> iau:_123456  skos:prefLabel   'rayonnement infrarouge' @fr
> iau:_123456  skos:altLabel   'émission infrarouge' @fr
>
> Note that I deliberately used some opaque string for the concept  
> URI, to make clear that this is a question concerning labels and  
> not concepts themselves. There is only one concept here, with four  
> labels.

This is not a minor point on another line-of-thought: the present IAU/ 
IVOA thesaurus proposal assumes that the token (Bernard's concept  
URI) is assumed to be the same as the preferred label (Bernard's  
"opaque string") when the "_" are replaced with spaces.    I think  
this is a good idea, but everyone should be clear that this is my  
assumption when looking at the normative text file.

> 2. A different issue arises when two different authorities have  
> issued vocabularies and you want to declare a posteriori  
> equivalence of such concepts. SKOS does not prevent you to use  
> owl:sameAs to express such an equivalence, since skos:Concepts are  
> individuals. If you look e.g. at http://www.geonames.org/ontology/ 
> ontology_v2.0_Lite.rdf, you will see that I have defined here a few  
> owl:sameAs equivalences between geographical feature codes (a  
> subclass of skos:Concept) and concepts defined by the environmental  
> GEMET thesaurus (also in SKOS).
>
> So something like the following would be perfectly consistent with  
> both OWL and SKOS semantics
>
> iau:stars   rdf:type   skos:Concept
> cds:stars   rdf:type   skos:Concept
> iau:stars   owl:sameAs   cds:stars

It's the "sameAs" functionality which we need to be able to translate  
between vocabularies.  Right now, we  haven't really begun to address  
this point in the context of the IAU/IVOA thesaurus, simply because  
we haven't addressed the point of multiple vocabularies.   A set of  
"SA" (for "same as") entries is quickly made if there is any point.    
For example, connecting to UCD1+ should be a major goal.

Assuming that the "SA" entries can be made in the tentative texts  
files, e.g.


	telescopes
		D
			"telescopes"
		SA
			ucd:instr.telescope

(or whatever), what format do we use for the SKOS versions?   Again,  
it would be nice to have a skeleton SKOS and skeleton OWL entry for  
the rest of us.

> Of course, you might want things more subtle than that, because for  
> some reason you want to declare a mapping without merging the two  
> concepts. In that case you can use SKOS mapping properties, but  
> note that this draft has no formal status whatsoever so far on W3C  
> track. See http://www.w3.org/2004/02/skos/mapping/spec/

Sigh.

> Hopes that helps

It does, thanks!   This is all very interesting (seriously!), but it  
should be clear that there's no way we're going to be able to produce  
a version of the IAU/IVOA where the ontological hints have been clean  
up / checked.   We should consider the present content to be  
informative and condusive to testing ontological analyses with  
thesauri.  The goal might be to go back and re-check the BT's, NT's,  
and RT's and maybe even add more info in the next version (or an  
auxilliary version).

In the meanwhile, we'll have a vocabulary to play with.

Rick

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Dr. Frederic V. Hessman     Hessman at Astro.physik.Uni-Goettingen.DE
Institut für Astrophysik          Tel.  +49-551-39-5052
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