STC in VOResource records

[Ray Plante]

On Wed, 3 Jan 2007, Arnold Rots wrote:
> Hm, if I read the definition of xs:ID correctly, even slashes and
> colons are not allowed.

Dang it--you are correct.  (Arnold, wouldn't want to save me from this 
hell? ;-)

Okay--here's a revised ruling--please find any remaining mistakes!
For reference, the problem being addressed is summarized in
http://www.ivoa.net/forum/registry/0612/1764.htm.

A publishing registry shall be responsible for creating IDs within STC
descriptions which are globally unique.  The convention for doing this
will be to use an ID of the following form:

     <resource's authority id>_<resource's resource key>_<coordsys key>

where all slashes are substituted with dashes (-) or underscores (_). 
For example, if the resource being described has an IVOA id of
"ivo://adil.ncsa/adil", then the following can be used as an internal STC
id refering to the UTC-FK5-TOPO standard system:

     adil.ncsa_adil_UTC-FK5-TOPO

The STC snippet, then, would look like this:

      <stc:STCResourceProfile
           xmlns="http://www.ivoa.net/xml/STC/stc-v1.30.xsd">

         <AstroCoordSystem xlink:type="simple"
                           xlink:href="ivo://STClib/CoordSys#UTC-FK5-TOPO"
                           id="adil.ncsa_adil_UTC-FK5-TOPO"/>

         <AstroCoordArea coord_system_id="adil.ncsa_adil_UTC-FK5-TOPO">
            <AllSky/>
         </AstroCoordArea>

      </stc:STCResourceProfile>

If you have objections to this, please speak up now.

I will note that I have discussed with Arnold a change to the STC schema
which would, for practical purposes, eliminate this problem in the context
of the registry (and other similar applications like VOEvent).  This
alternative was suggested in part by Ed Shaya (see
http://www.ivoa.net/forum/registry/0612/1773.htm).  It uses XLink for both
internal and external linking.  In the rare case in which a non-standard
coordinate system were described (rather than simply referenced) then the
above convention would, in principle, still need to be invoked.  Arnold is
mulling this idea over.

cheers,
Ray