Re: On clarification for getCapabilities and stageData

Pedro, Doug,

I share Pedro's worries -- in the original IVOA design VOQL/ADQL was presented as a language which would be generally used to locate/select the available data in the various IVOA components (directly from servers or through registries). The various DAL realisations seem to include now querying facilities -- I would however call these 'filtering capabilities' since these are used to restrict the interesting set of 'files' to the user's wishes.

Some clarification between the roles of -- this 'filtering capabilities' applied to tabular material

   discussed by Doug
-- the query language (more than just a filtering operation) -- the TAP itself
seems to be necessary.

--Francois

>
>Hi Pedro -
>
>This topic - the new DAL service profile, including getCapabilities
>etc. - goes back to at least the 2006 interop in Victoria, where it was
>discussed in the full DAL sessions and in the plenary. The approach is
>based on OpenGIS and was built into the SSA protocol about that time.
>We (you and I) have also discussed these issues in connection with
>SLAP, with the conclusion that SLAP would wait to update to the new
>service profile and getCapabilities, after it was developed and tested
>within SSAP.
>
>It is true that the most recent discussion of service metadata
>and getCapabilities has been mostly between Ray and myself (as the
>Registry and DAL chairs) over the past several months. However,
>this discussion has thus far mainly been on the high level issues,
>such as the scope of service metadata, and these have had adequate
>exposure elsewhere, most recently in the TEG forum (where this has come
>up repeatedly, e.g., in the description of the DAL service profile).
>The related issue of dataset metadata, and the relationship between
>service and dataset metadata, has also been discussed. Thus far,
>I have seen almost no response from the TEG to anything of this sort
>which I have posted.
>
>Given that this overall approach has been out for discussion for about
>a year, and is now implemented in actual protocols and implementations
>(SSAP), I can't see making major changes at this point. The details
>of what getCapabilities contains and how it is used, however, are
>still open for discussion. As I say, we have a session dealing with
>getCapabilities scheduled for Beijing (DAL-1), where Ray and probably
>some other registry folks will be present.
>
>Regarding stageData, the concept for this has been out since SIA 1.0;
>there is a section on it in the SIA specification. It has never been
>implemented as we have not had the low level technology available to
>do so. The role of this in the DAL service profile is well established
>at this point, however the details are still TBD, and are now being
>considered. The concept was gone into in some detail again within
>the TEG in the TAP design study which I posted earlier this month.
>It was also discussed in the GWS list a month ago in connection with
>the REST discussions. There has been additional discussion in the
>past week, most of it in the context of the IVOA Assessment over the
>past week, which you will have seen (I also copied a section of this
>to the TEG as a heads-up). Guy, Matthew, and myself have had a bit
>more discussion in private emails as well. We plan to continue this
>in the DAL and GWS sessions in Beijing.
>
>Substantive discussion of this would be welcome. There is plenty of
>material out there to review, and has been for some time.
>
> - Doug
>
>

Francois Ochsenbein       ------       Observatoire Astronomique de Strasbourg
   11, rue de l'Universite F-67000 STRASBOURG       Phone: +33-(0)390 24 24 29
Email: francois-at-astro.u-strasbg.fr   (France)         Fax: +33-(0)390 24 24 32
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