New version of the SIA V2.0 PR

[Bruce Berriman]

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