Ontology-based queries

[Tony Linde]

Based mainly on what Sean has said, is it correct to say that, given a
reasonable AstroOntology, if I want to find:
 
 Object is-of-type SNR
  AND Source registers-in-wavelength X-Ray

what the interpreter does is to formulate a class of the above type and
then find all objects which are instances of subclasses of that class,
whether explicitly or implicitly stated to be so.

If my supposition is correct, it seems that an ontology-based approach
to querying a registry would have significant benefits here since we
don't need to make sure that objects are classified in every way that
they might be queried. SQL queries of this type are notoriously
difficult to code and get to work efficiently.

On the other hand, if we modify the above query to be:

 Object is-of-type SNR
  AND Source registers-in-wavelength X-Ray
  AND Object is-within (1 arcmin) of-region (05 25 00 -69 38)

I think we hit difficulties. I cannot see how an ontology-based query
like this could work.

Is this right? Or am I trying to compare apples and oranges?

Cheers,
Tony. 

__
Tony Linde                       Phone:  +44 (0)116 223 1292
AstroGrid Project Manager        Fax:    +44 (0)116 252 3311
Dept of Physics & Astronomy      Mobile: +44 (0)7753 603356
University of Leicester          Email:  tol at star.le.ac.uk
Leicester, UK   LE1 7RH          Web:    http://www.astrogrid.org