WD-SIA-2.0-20140512 available

[Douglas Tody]

Hi Walter -

You may get differing responses to your query, but the intent of SIAV2,
and V1 for that matter, has always been to provide clients with remote
access to image data, i.e., the "image access" in SIA (rather than mere
discovery/download of whole images).  In V2 much of the advanced
client-directed data access capability, such as for slicing cube data,
has moved to AccessData.  For reasons that are largely pragmatic
AccessData is now a separate specification, but logically SIAV2 and
AccessData are both part of the V2 image access capability.

Support for simple image mosaic (and cutout) capabilities is an
important capability that is not currently adequately addressed.  As you
say this capability has been in V1 for over ten years now.  In principle
an SIAV2 interface could describe a virtual image such as a cutout or
mosaic, however there is no support for this in the current
specification, and the critical spatial query portion only provides a
simple discovery capability for static archival images (the concept of
the "ideal image" has been dropped).

If people want these capabilities - speak up.  We already do all these
things in prototype interfaces, but there has not been sufficient
agreement to include such capabilities in the V2 specification.

 	- Doug


On Wed, 14 May 2014, Walter Landry wrote:

> Patrick Dowler <patrick.dowler at nrc-cnrc.gc.ca> wrote:
>>
>> (on behalf of Doug as well)
>>
>> The latest SIAv2 working draft is available; I hope all issues
>> discussed on the mailing list have been addressed.
>>
>> http://www.ivoa.net/documents/SIA/
>
> I am a bit confused about the intent of SIA v2.  In the abstract, the
> draft talks about data cubes, but the text does not any general
> support for selection that, for example, AccessData has.
>
>  http://wiki.ivoa.net/internal/IVOA/AccessData/WD-AccessData-1.0-20140312.pdf
>
> To be precise, AccessData provides a way to select a slice in an
> arbitrary coordinate (e.g. redshift) with the COORD parameter.  I do
> not see anything comparable in SIA v2.
>
> I am fine with SIA v2 not supporting this kind of thing, but I just
> wanted to clarify the intent.
>
> Also, SIA v1 had support for mosaic services.  I have been looking
> through the mailing list, but I have not found a definitive answer.
> Is support for mosaic services a non-goal for SIA v2?  If so, perhaps
> that should be mentioned in the introduction?
>
> Thanks,
> Walter Landry
>