On Wednesday 30 May 2007 14:59, Doug Tody wrote:
> The first question asked was what SIAP 1.0 intended, and this is what
> I have addressed above. SIAP has always worked this way, and I am
> surprised that anyone is confused.
I don't think the FORMAT thing in SIA 1.0 is confusing. For most people, I expect, the collection they are serving is in one format or they decide to serve one format, so if a query comes in asking for GIF and they only have FITS, they return an empty VOTable (this is what we do).
We have also toyed with on-the-fly conversion, which if deployed would mean we could respond "yes" to any format and do the conversion in the getData stage. This and the above approach are both kind of "a priori" knowledge of the possible types, without doing a DB query.
We also have in some cases pre-computed preview images in graphics format, but I always found it kind of ugly for the observation catalog to know about these different formats. Essentially, trying to support this in a really general way brings in a very large database denormalisation problem, especially when you have set of systems for storing all the files and another for enabling the querying of metadata. I prefer to leave the file type stuff for the delivery mechanism to handle (eg the getData method) since that can be largely independent of the querying (except in this case of formats).
if one had the on-the-fly conversion in place, then pre-computed previews (for example) could be just an optimisation of the retrieval process, which is again nice and clean and simple. But in general I think this FORMAT thing is an optimisation that introduces some complexity to implementing the service in some cases. It is easy enough to avoid that by reducing the scope of the service (eg we have fits and jpg but only deliver fits because we don't always have jpg on hand) but that does reduce overall value.
summary: it's more complicated than it looks, but not confusing :-)
-- Patrick Dowler Tel/Tél: (250) 363-6914 | fax/télécopieur: (250) 363-0045 Canadian Astronomy Data Centre | Centre canadien de donnees astronomiques National Research Council Canada | Conseil national de recherches Canada Government of Canada | Gouvernement du Canada 5071 West Saanich Road | 5071, chemin West Saanich Victoria, BC | Victoria (C.-B.)Received on 2007-05-31Z01:15:26