Multi-dimensional Data Access minimal requirements

[Arnold Rots]

Mark,

This set of requirements is for a simple subset.
I think it would be fair to apply the same criterion to the redshift axis:
don't cover the complicated stuff you are listing - multiple lines,
multiple objects, etc.

Just a simple redshift axis, only allowing a single restfrequency (on the
spectral axis),
with Doppler definition (OPTICAl, RADIO) and reference position (TOPO, GEO,
BARY, LSR).

After all, these requirements don't propose the spatial axes because a
full, complicated
REGION syntax cannot be implemented ;-)

Cheers,

  - Arnold

-------------------------------------------------------------------------------------------------------------
Arnold H. Rots                                          Chandra X-ray
Science Center
Smithsonian Astrophysical Observatory                   tel:  +1 617 496
7701
60 Garden Street, MS 67                                      fax:  +1 617
495 7356
Cambridge, MA 02138
arots at cfa.harvard.edu
USA
http://hea-www.harvard.edu/~arots/
--------------------------------------------------------------------------------------------------------------



On Fri, Mar 7, 2014 at 4:08 PM, Mark Allen <mark.allen at astro.unistra.fr>wrote:

> Hi Arnold,
>
> I'm glad to hear you consider the requirements generally reasonable!
>
> I'm aware of the discussions about redshift/Doppler and spectral axes. The
> distinction I make here is that redshift/Doppler velocity is an interpreted
> coordinate that requires extra information (Doppler definition opt/radio, a
> redshift, or a reference frequency/wavelength - as you've pointed out in
> those discussions) and that the definition of those extra things is
> sufficiently complicated to leave it out of this first cut of requirements
> for data cubes.  Multiple objects, or multiple spectral lines in a given
> cube come to mind as complications let alone identification of redshifts of
> individual objects.
>
> That said, I agree that being able to distinguish different sorts of data
> cubes in data discovery is important and we should discuss this as part of
> the next steps - there can be many other cube axes that we would like to be
> able to query on and I suggest that Redshift/Doppler cube axes be part of a
> wider consideration of interpreted and derived axes in the next steps.
>
> best regards,
> Mark
>
>
> On 7 Mar 2014, at 16:27, Arnold Rots <arots at cfa.harvard.edu> wrote:
>
> While appreciative of these requirements that are generally reasonable,
> I have to register my strong objection to its leaving out the Doppler
> velocity
> (Redshift) axis. I have said this over and over, and will keep repeating
> it:
> if we don't properly distinguish between the redshift and the spectral
> axes,
> queries and results will get confused and users annoyed.
> Redshift or Doppler velocity constraints need to be added to Data Discovery
> and to Simple Cutout.
>
> Cheers,
>
>   - Arnold
>
>
> -------------------------------------------------------------------------------------------------------------
> Arnold H. Rots                                          Chandra X-ray
> Science Center
> Smithsonian Astrophysical Observatory                   tel:  +1 617 496
> 7701
> 60 Garden Street, MS 67                                      fax:  +1 617
> 495 7356
> Cambridge, MA 02138
> arots at cfa.harvard.edu
> USA
> http://hea-www.harvard.edu/~arots/
>
> --------------------------------------------------------------------------------------------------------------
>
>
> Mark Allen
> mark.allen at astro.unistra.fr
>
>
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