Call for proposals for SIAP Version 2

[Steve Lowe]

John Good wrote:

>Roy -
>
>  
>
>>> Galactic coordinates are pretty important and adding support
>>>for these to POS is a reasonable thing to consider.
>>>      
>>>
>>The more complicated is the specification of conesearch/SIA, the smaller the
>>number of implementations! It is the NVO that should build the middleware --
>>so that users get a rich set of services, but the entrance cost for
>>publishers is low low low.
>>
>>One way to do the galactic coordinates is to specify SIA in terms of a
>>single coordinate system (as it is now), and have a middleware service to
>>make the coordinate conversion, which in turn calls the elementary service.
>>    
>>
>
>This is dead wrong.   Coordinate syntax parsing, coordinate transforms,
>and polygonal constraints (which includes the "cone search" as a single-
>constraint subset) are all straightforward and should be an integral part
>of any server-side search engine (image or catalog).  NVO should be
>promulgating knowlege on how to do this (and portable code snippets,
>where appropriate), not characterizing it as a complex issue that needs
>third-party middleware.
>  
>
Coordinate transforms are not difficult, but they're not trivial to get 
right either. This is especially so if we depart from the "distant" sky 
and try to specify more local observations for which the observing 
position is important.

While I generally agree with the philosophy of providing know-how rather 
than software, I think realistically it will be beneficial to keep the 
buy-in cost low as Roy suggests. Consider that the user receives the 
direct benefit in acquiring data from a provider. The provider's 
benefit, if any, may be more indirect, such as community publicity or 
favor of the funding agencies. This is an argument for making life as 
easy as possible for the provider.

I don't think portable code snippets will do, I think you'd need a 
supported software library.

Whatever the ultimate decision on whether clients or providers have to 
support multiple coordinate systems, for now this capability can be used 
as a model to examine client-provider negotiation.

Steve

-- 
Steve Lowe
Smithsonian Astrophysical Observatory
Harvard-Smithsonian Center for Astrophysics
slowe at cfa.harvard.edu
1-617-496-1661