Multi-dimensional Data Access minimal requirements

[Douglas Tody]

On Tue, 11 Mar 2014, Ray Plante wrote:

> On Tue, 11 Mar 2014, Robert J. Hanisch wrote:
>> Remember, too, we are talking about the query that gets sent from the
>> interface to a service.  SIAP queries will most likely result from web
>> forms or programmatic interfaces in which user-friendly inputs can be
>> specified.  So we need not make the range specification so dumbed-down as
>> "circle".
>
> Recalling that this question arose from the requirement for supporting
> simple cut-outs, we should clarify where the use of circle/range would
> appear.  I'm gathering from Pat's response that this something that
> goes specifically into AccessData, and would not affect image
> searching, which is handled by SIAv2.  Is this correct?

As I think Pat stated, the current thinking is that POS,BAND,TIME,POL
would be similar or identical for both the discovery query and for
accessData (more advanced slicing/dicing would require
accessData-specific custom parameters).

> This reminds me of another related question.  SIAv1 had the feature
> that allowed a service to bill itself specificially as a "cutout"
> service, which meant that the search queries would specifically return
> images that are cut-outs matching (as close as possible) the search
> region.  Is this expected to be allowed/supported by SIAv2?

This is what we have been calling automated virtual data generation
(AVDG); it was discussed extensively in an earlier thread.  As in SIAV1,
one just specifies the usual region of interest (e.g., POS,SIZE or some
more complex POS object as Pat has proposed), with mode="cutout".  That
is, POS[,SIZE],mode=cutout is equivalent to the "cutout" service we had
with SIAV1.  Rather than have two or three different flavors of SIA
services for archival images, cutouts, or mosaics, one has a single
service with a MODE parameter.

If one think's about the details, automated cutouts (or mosaics) of this
sort are much more convenient and practical for a client than trying to
do it all with an explicit series of calls to queryData, getMetadata,
accessData.

For example, imagine we have a wide-field survey with full coverage of a
large region of the sky.  We want a cutout service.  We no longer care
much about the individual images since we have full coverage; it is as
if we have one large virtual image covering much of the sky.  If the ROI
we are after falls, e.g., at the corner of 4 images, each with a
slightly different overlapping coverage and projection, it would be
quite tricky to generate the desired image client-side with low level
calls.  With the 12-year old SIAV1, it is just a simple POS,SIZE query
to a cutout service.

 	- Doug