multiple capabilities of the same kind

[Ray Plante]

Hi Paul,

Thanks for bringing this up.

On Fri, 15 Feb 2008, Paul Harrison wrote:
> We have recently come across people wanting to register services with 
> multiple capabilities of the same kind e.g. a resource with two capabiities 
> whose standardID="ivo://ivoa.net/std/SIA",

One thing that would be important to know here is what is it that the 
registrant is trying to accomplish by doing this?  What is it that is 
distinction between the two SIA capabilities.  By being part of the same 
resource, it is presumed that both access the same underlying data. 
Assuming this is true, it could be that the capabiliity metadata is 
different; if so, why?  If it is simply a matter of providing multiple 
base URLs for the endpoint of the service, then this can be provided as 
multiple <accessURL> elements withing the <interface>.

> OR
>
> We amend the VOResource schema and add an extra "name" attribute onto the 
> capability element, which could be used to distinguish between multiple 
> capabilities with the same standardID by using the value of the name 
> attribute as the URI "fragment" e.g. ivo://org.mytelescope/survey#rband could 
> be used to identify the individual simple image access capability within the 
> resource.

This is an interesting and appealing idea; however, I note that VOResource 
has already passed to recommendation.  Thus, this change would have to be 
handled as a new version of the standard and passed through the process 
from WD.  Given this, I would recommend that we deal with this cases with 
the schema we have.

So, let's first determine what is intended by this use case.  If there is 
not already an existing mechanism for dealing with the use case, then we 
should, for the moment as a matter of policy, recommend registering the 
SIAs as separate resources.

cheers,
Ray