[QUAR] Re: Expressing position in RDF

[Matthew Graham]

Hi,

I'm happy for the philosophical discussion but am also trying to  
figure out how to actually do something empirical. I can see exactly  
the same arguments that we had about using STC in VOEvent applying to  
representing positions in RDF. The 90:10 rule should apply and whilst  
it is wonderful that I can describe any position in any coordinate  
system using ontology X, why can't we have ontology Y that is small  
and simple (that word again):

:myStar stc:UTC-TOPO-FK5#RA 134.56

	Cheers,

	Matthew

On Oct 14, 2008, at 11:47 AM, Rob Seaman wrote:

> Bernard Vatant wrote:
>
>> how do you attach measurement results to an object?
>
> This is begging the question in an observational science.  The  
> existence of the object is the null hypothesis you're trying to  
> test.  Anyway, I don't think Matthew was looking for a philosophical  
> discussion :-)
>
> But if you did want to pursue this, one might suggest starting with  
> the distinction between the dependent and independent variables of  
> the observation/measurement.
>
>> Seems to me the scientific community (at least its members involved  
>> in Semantic Web) should try and standardize this at some point.
>
> This is the center of the scientific maelstrom.  One might have  
> better luck first looking elsewhere.
>
>> I've been looking for relevant pointers to people working on this  
>> in other domains (say e.g., Biology, Earth sciences ...) without  
>> much success so far I'm afraid.
>
> Returning to the question at hand, this is an interesting point.  We  
> act as if astronomical coordinates are particularly difficult.  They  
> are, in fact, particularly well behaved.  Things tend to stay put on  
> the celestial sphere (for many purposes).  Imagine building the same  
> assertions for - say - wildlife management.  A herd of caribou  
> doesn't stand still.
>
> One may, however, make assertions - as with stars - about the  
> temperature of a particular caribou or other parameters such as sex  
> or mass or age.  These are assertions inherent in the object  
> itself.  One may make assertions about group behavior - a "cluster"  
> of caribou.  One may make assertions about evolutionary descent.
>
> But it is orders of magnitude more difficult to specify location  
> (longitude and latitude as a function of time) for caribou than it  
> is for stars.  And in astronomy, one is typically expressing  
> targeting coordinates (explictly or implicitly) for future  
> observations.  On the other hand, predicting the future migrations  
> of caribou is simply impossible.
>
> It seems unremarkable to me that an assertion in an astronomical  
> context (say, stars), might look something like:
>
> 	X is a star
> 	X corresponds to target Y
> 	Y has WCS Z
> 	Z has an RA (along with a bunch of other attributes) - and  
> corresponding to some fiducial point like the centroid of a PSF
>
> Compare to:
>
> 	A is a caribou
> 	A is somewhere in Alaska
> 	Alaska has (complex and idiosyncratic) GIS data structure B
> 	B has a footprint the size of the lower 48 east of the Mississippi
>
> Rob
>