SIAPv2 address

[Douglas Tody]

Hi -

Note that the document referred to below is not a draft specification,
but rather a concept document.  You can also find it via the "image
access" topic link from the main DAL wiki page.

Anita - thanks for the detailed comments, they are the most thorough
anyone has provided so far.  I am on travel now but will try to follow
up on some of your points by Monday.

The SIAV2 concept discussed in the document is basically the same as
SIAV1, but generalized to N-D (as in  FITS).  In particular the ability
to access data cubes is added, which is especially needed for the very
large spectral data cubes coming soon from modern radio telescopes and
surveys.  The 2-D capabilities are much the same as for V1, but with
an updated DAL2 interface (based upon subclassing the generic dataset)
similar to SSA except for where it is specialized for image access.
Async capabilities are included and are expected to use the UWS-based
approach being worked out for TAP, which will become part of the
DAL2 interface profile.  The query and basic acref-based retrieval
are (normally) synchronous as at present, but an ability is added
to initiate an optional async job to create and stage one or more
images, based upon the specifications established in a prior query.
This will enable complex image generation as well as multi-position
queries, e.g., to create cutouts for many object positions.

But basic 2-D access remains pretty simple - a simple POS,SIZE query
followed by one or more GETs to retrieve individual images will
still work.

 	- Doug


On Sat, 21 Mar 2009, Anita M. S. Richards wrote:

>
> For information, the version of SIAPv2 which I commented on is at
>
> http://www.ivoa.net/internal/IVOA/InterOpOct2008DAL/siav2-oct08.pdf
>
> (I did not make it to the interop which is why this is the first I ahve seen 
> of it - perhaps as general practice, we should try and locate links to 
> docjments from WG pages or something also? - I am sure that I am equally 
> guilty of obscuring things, though...)
>
> thanks
> a
>
> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
>
> Dr. A.M.S. Richards, UK ARC Node/AstroGrid,
> Jodrell Bank Centre for Astrophysics, Alan Turing Building, University of 
> Manchester, M13 9PL
> +44 (0)161 275 4124
> and
> MERLIN/VLBI National Facility, Jodrell Bank Observatory, Cheshire SK11 9DL, 
> U.K. +44 (0)1477 571321 (tel) 571618 (fax)
>
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>