Astronomical vocabulary explorer

[Norman Gray]

Franck, hello.

On 2008 May 3, at 16:28, Franck Le Petit wrote:

> 	We are building a vocabulary that will be used in the Simulation  
> Datamodel.  Semantics is required for several "keywords":
> 	- Physical processes
> 	- Algorithms
> 	- Simulated Object
> 	- ...

> 	May you tell me what is the best way to implement this ? Should we  
> do .RDF files ? And if yes, is there any tool to do it easily, I  
> mean to facilitate the entries and the relationships between words ?

The semantics group is currently discussing a document which aims to  
give precisely this sort of advice.

The current Working Draft document is at

     http://www.ivoa.net/Documents/WD/Semantics/vocabularies-20080320.html

and the current "editors' draft" lives at

     http://www.astro.gla.ac.uk/users/norman/ivoa/vocabularies/

(I've just today released a fairly significant update to that).   
Summarised, it says that yes, RDF is good for this, and that  
specifically there's a framework called SKOS, which is intended to  
support precisely this sort of vocabulary.  I'd be very keen to hear  
your comments on the intelligibility and user-friendliness of this  
document, if you have time.

Vocabularies are at the lightweight end of the ontology spectrum, and  
SKOS vocabularies in particular are concerned with rather thin  
semantics such as which terms are broader or narrower in scope than  
others.  The sort of ontologies that Ed is talking about are more  
expressive -- you can do more with them -- but they're correspondingly  
more expensive to create and broker agreement on.

The most practical approach, I think, is to find a vocabulary that is  
reasonably close to what you need, and use that as much as possible.   
Creating a vocabulary (or ontology, or schema, or DTD) is easy;  
creating one that a useful number of other people agree on is very hard!

The vocabularies that are distributed with the above WD (a snapshot of  
which you can download as a bundle at <http://www.astro.gla.ac.uk/users/norman/ivoa/vocabularies/rdf/vocabularies-2008-05-08.tar.gz 
 >) were generally produced by starting with an existing vocabulary in  
some semi-regular format, and writing a per-vocabulary script to  
regularise that into RDF.  That is, we didn't actually need to use a  
GUI tool at any point, though I'd agree with Ed's remarks about the  
appropriateness of Protégé.

Best wishes,

Norman


-- 
Norman Gray  :  http://nxg.me.uk
Physics and Astronomy, University of Leicester