content, format, ctype, or xtype ?

[Douglas Tody]

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