content, format, ctype, or xtype ?

[Arnold Rots]

To answer you last comment: I wasn't specifying how the query should
be phrased, only the content. Btw, remind me: SIZE is in angular
units, right, not in coordinate units? In which case POS,SIZE wouldn't
work.

I don't disagree with Tom. My concern was that servers would implement
common non-ICRS queries correctly and efficiently. That concern was
fed by a service I once saw that transformed the corners of such an
(l,b) query to (RA,Dec) and then performed the query on max and min of
those coordinates :-(

  - Arnold


Douglas Tody wrote:
> On Fri, 15 May 2009, Tom McGlynn wrote:
> >
> > The question that I think we should be posing is what capabilities do we 
> > provide the user in querying the system and in seeing the results.  The 
> > internals of how one site stores things internally is something that we might 
> > chat about, but I don't see that it should be mandated or even discussed in 
> > the standard.
> 
> Whether data providers do this by adding new columns or by adopting
> the guidelines when a table is first created should be up to the
> data provider.  Most would probably choose to add columns in the case
> of old tables, but they might also adopt the guidelines directly
> when designing new tables.  Whether they compute the data on the
> fly or store the data directly in the tables does not matter, that
> is a back-end implementation issue.  Compliance should be optional
> but recommended.
> 
> > Arnold Rots wrote:
> >> Here is the issue:
> >> If a user queries a catalog for, say 90 < l <270 AND -30 < b < 30
> >> you have to do an on-the-fly transformation of almost all your RA,Dec
> >> entries in order to make sure you get the right subset.
> 
> Why not just do this properly with a TAP spatial query (POS,SIZE,
> REGION, etc.).  This is simple for the client.  What happens on the
> server side is up to the service.  It will eventually come to proper
> spatial indexing and careful coordinate transformations on the server
> side, if we try to do very much with such spatial queries.
> 
>  	- Doug
> 
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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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