[QUAR] Re: Expressing position in RDF

[Arnold Rots]

Matthew Graham wrote:
> 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  

No, it shouldn't - because you'll paint yourself into a corner that will
never allow you to address the remaining 10%.

> 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
> >
> 
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Arnold H. Rots                                Chandra X-ray Science Center
Smithsonian Astrophysical Observatory                tel:  +1 617 496 7701
60 Garden Street, MS 67                              fax:  +1 617 495 7356
Cambridge, MA 02138                             arots at head.cfa.harvard.edu
USA                                     http://hea-www.harvard.edu/~arots/
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