SSA extension schema

[Doug Tody]

Hi Ray -

I missed this old email earlier as it was posted during the interop.

My suggestion would be to use a different xsi:type for the early
prototype spectrum services: although both return spectra, this was
really a different interface, and not a version of the SSA interface.
I am concerned that few client applications looking for SSA services
will bother to query on the version number, and may fail in trying to
query these older services since the interface is completely different.
A different capability type allows both types of services to be found,
with a simpler query, and without risking confusing the two.

	- Doug



On Mon, 24 Sep 2007, Ray Plante wrote:

> Registry providers and SSA enthusiasts,
> 
> One of the things we'll talk about this week in Cambridge is support
> SSA services in the registry.  I've been discussing an VOResource
> extension for SSA with Doug Tody and Markus Dolensky.  There is draft
> schema being considered; however, there are still some issues to be
> worked out.  Nevertheless, there is quite a bit of demand to support
> current SSA implementations in the registry as soon as possible.
> 
> I've set up a twiki page for discussion of this schema.
> 
> http://www.ivoa.net/twiki/bin/view/IVOA/SsaResourceSchema
> 
> You will find two versions of the schema on that page:  one that has
> all of the elements that are currently desired in the extension,
> including those that still need further discussion and consideration.
> The second is a working draft being put forward for immediate
> support which has the unstable bits removed.  If we adopt this version
> now, it is expected that we would migrate to a final 1.0 version in 3
> to 6 months.
> 
> One important issue we need to address is how to support the earliest
> SSA implementations.  These were built well before v1.0 of the SSA
> spec was completed; thus, it is unlikely that they would be compliant
> at this time.  Still, several do exist, and it would be good to
> recognize these as serving spectra.
> 
> VOResource v1.0 allows one to list in one resource description support
> for different versions of a protocol.  For SSA, this means that within
> the "SimpleSpectralAccess" capability element, multiple interface
> elements may be listed, each with a different value for its version
> attribute.  (If version is not provided, "1.0" is to be assumed.)  I
> recommend that we encourage the registration of the early SSA services
> using the "SimpleSpectralAccess" capability but to set the value of
> the interface element to "proto".  That is,
> 
>    <ri:Resource ...>
>       ...
>       <capability xsi:type="ssa:SimpleSpectralAccess">
>          <interface xsi:type="vs:ParamHTTP" version="proto">
>             <accessURL> ... </accessURL>
>          </interface>
>          ...
>       <capability>
>       ...
>    </ri:Resource>
> 
> (If you don't "proto" as a version string, please suggest an
> alternative, e.g "0.5".)
> 
> cheers,
> Ray
>