New version of the SIA V2.0 PR

[François Bonnarel]

Hi all,
      Discussion on the topics raised by Walter took place in Banff and 
also in some cases before on the mailing list and the RFC page.
     Some of Walter's proposals have been clearly identified to get 
solution in next version of SIAV2 or in AccessData.
     The RANGE issue and current draft syntax issue got less interest in 
the discussion in Banff and were discussed previously. Private 
discussions those days seem to show that to some points ideas cannot 
totally converge and  what we need now is practical "proof of the concept".
      I am confident from other private discussions that two reference 
implementations will be soon described on the RFC page. This can be a 
way to go further in the process of modifications/achievment.
      By the way I propose to start the TCG review with the current 
version of the PR on Monday. This will also put new in puts from other 
Working groups.
Best regards
François Bonnarel

Le 03/11/2014 20:36, Walter Landry a écrit :
> For RANGE, I did not get any feedback beyond what is on the wiki.  For
> syntax, there was a fair amount of interest in my new implementation
> but no one was willing to commit to a new order of things.
>
> Cheers,
> Walter Landry
>
> Bruce Berriman<gbb at ipac.caltech.edu>  wrote:
>> Thanks - now, did you receive any feedback after your talk on the two issues below?
>>
>> Cheers
>>
>> bruce
>>
>>
>> On Nov 3, 2014, at 10:38 AM, Walter Landry<wlandry at caltech.edu>  wrote:
>>
>>> Hello Everyone,
>>>
>>> I have discussed my issues with SIA v2 in other forums, but I was told
>>> I should express them here for the TCG.
>>>
>>> As background, I tried to implement an SIA v2 service for a virtual
>>> image service for the Planck satellite.  This is a use case that SIA
>>> v1.0 covered well with its support for Image Mosaicing Service, but
>>> now seems to have been split off into AccessData.  I gave a talk about
>>> my experience at the Banff Interop [1], so this email is a
>>> distillation of the problems I found.
>>>
>>> 1) RANGE
>>>
>>>    Section 2.1.1 includes a RANGE shape.  A RANGE is not a square on
>>>    the sky, but users could easily think that it is.  This makes it
>>>    error-prone.
>>>
>>>    Also, a RANGE shape is significantly different from the other two
>>>    types, so it could be a non-trivial amount of work to implement.
>>>    In my particular case, it was enough work such that I did not
>>>    implement it, though I did implement CIRCLE and POLYGON.  This is
>>>    in contrast to something like a BOX shape, which only requires
>>>    transforming the BOX into an equivalent POLYGON.
>>>
>>>    Finally, the only use case that I have heard for RANGE is for
>>>    tiling the sky.  However, tiling the sky is fairly easy with a
>>>    POLYGON.
>>>
>>> 2) Syntax
>>>
>>>    SIA v2 invents yet another syntax.  This creates an unnecessary
>>>    burden on both implementors and users.  The syntax that was chosen
>>>    is also error-prone.  We should reuse an existing syntax.  In my
>>>    presentation [1], I presented my work on using Javascript syntax.
>>>    It preserves the simplicity of key-value parameters while scaling
>>>    to extremely complex inputs.  But whatever is decided, please do
>>>    not invent a new syntax.
>>>
>>> Cheers,
>>> Walter Landry
>>>
>>>
>>> [1] http://wiki.ivoa.net/internal/IVOA/InterOpOct2014DAL/Wlandry_DAL_I.pdf