IAU thesaurus in RDF (an update)

[Rob Seaman]

On Oct 5, 2007, at 8:42 AM, Arnold Rots wrote:

> This hit a nerve: the 21 cm hyperfine line of neutral atomic hydrogen
> is NOT a recombination line.

The late David Van Blerkom would be distressed that I read right past  
that blooper.  I don't know whether to feel vindicated or mortified  
that it's present in the original blessed IAU list.  This is another  
value that vetting by IVOA can bring to the IAU.

More fundamentally, this seems to me to be a limitation of the word  
"thesaurus" as applied to narrow domain specific vocabularies.  When  
Roget tells us that "line" can map to vastly diverse terms like  
"delineation", "wrinkle", "drain", "queue", "rope", "profession",  
"pedigree", "postcard", "spiel", "commodity",  and so forth and so on  
- this is quite a different activity than establishing a hierarchy of  
radiative recombination lines and associated terms.  The word  
"recombination" isn't even recognized by Roget with any synonyms.

On the other hand, my central concern with ontologies is that it is  
trivially easy to build a nonsense hierarchy that permits neutral  
hydrogen to be filed away under recombination categories that require  
ionized species.  Hell, the word "species" means something entirely  
different in this context than what Darwin meant.

Ideally semantic tools will aid us in delineating physically  
meaningful relationships between newly discovered phenomena with  
unexpected - and often temporarily mistaken - explanations.  Until  
that time, I suggest any vocabulary list we publish - whether UCD,  
RDF, SKOS, OWL or plaintext - include words like "unknown" and "other".

- Rob