DAL sessions in Victoria

[Doug Tody]

Hi Silvia -

The basic SIAP query for the next version will be very similar to
the basic query defined for SSA - where we are headed is to make
the "generic dataset" metadata and query parameters the same for
all DAL interfaces.  In particular, the minimal query will permit
data selection based on the physical measurement axes which all
data shares: the spatial, spectral, and time axes (what to do about
things like polarization is still TBD).

As soon as one has multiple dataset attributes to query, there are many
valid queries and any of these become optional.  Hence POS,SIZE will
become optional for client queries, and services will be required to
support at least TIME and BAND as well as POS,SIZE,FORMAT.  There are
additonal new query parameters as well, e.g., minimum resolution in
any axis, or the object name especially for moving objects (these
more advanced parameters are generally optional for the service).

Despite the name, SSA is intended to support time series.  Both spectra
and time series are a photometric sequence; the spectral coordinate
is the variable for spectra, while for time series the time coordinate
varies, but most aspects of the data model are the same for both.

> I think that enabling some degree of interoperability between
> Astronomy and Solar System VOs is important. The science

I agree that we should encourage this, particularly at the level of
the technical infrastructure, recognizing that the data can often be 
quite different in the different domains.

 	- Doug


On Wed, 26 Apr 2006, Silvia Dalla wrote:

>
> Hi Doug,
>
> it's good to hear that the next version of SIAP will support
> queries by time. The question for the solar system (not just
> solar) community is whether or not POS and SIZE will be
> mandatory parameters. Essentially we need to have the capability
> of querying by time range *only* (I think that this kind of query
> may be useful also in some astronomy use cases ). Hence in the
> STAP proposal POS and SIZE are optional parameters.
>
> (Note that STAP assumes some friendliness of Votable to
> ISO-6801 time strings - see the recent post by Mark Taylor
> in the votable forum, and following discussion).
>
> I think that enabling some degree of interoperability between
> Astronomy and Solar System VOs is important. The science
> boundaries between these areas are becoming less and less sharp
> (Helio- and astero-seismology, solar and stellar flares, exoplanets,
> HST imaging the aurora on Jupiter and Saturn etc...).
> As you say, there are big differences in metadata and coordinate
> systems so this will necessarily be limited.
>
> AstroGrid are currently providing VSO data via the HelioScope
> service, which is based on STAP. I believe that Frank and VSO
> have expressed an interest in IVOA activities, specifically
> VoEvent.
>
> It will be good to discuss these issues further in Victoria,
> with best wishes,
> Silvia
>
>
> On Tue, 25 Apr 2006, Doug Tody wrote:
>
>> Hi Silvia -
>>
>> Thanks, that helps a bit to clarify things.
>>
>> Note that the next version of SIAP will support queries by time and
>> spectral bandpass as well as position (among other things). The main
>> reason for having a separate protocol for solar data would be if the
>> metadata required to describe solar data is significantly different. Here
>> in the US for example, the VSO (Virtual Solar Observatory) has their own
>> protocols which are tuned to their data. At the most basic level these are
>> similar to what we have in IVOA, but there are substantial differences,
>> e.g., position refers to the solar surface or the corona, the observed
>> attributes may include things like acoustic power or number of sunspots,
>> and so forth. The metadata returned to describe an image or other
>> observation would probably be substantially different. See for example
>> http://vso.nso.edu/.
>>
>> It is an interesting question for the IVOA whether its scope should
>> include solar and planetary data. Currently we don't really address this,
>> and these disciplines tend to already have their own "VO" (at least here
>> in the US). However, there is some contact and there are occasional
>> discussions about increasing interoperability or possibly sharing
>> technology.
>>
>>    * Doug
>>
>> On Tue, 25 Apr 2006, Silvia Dalla wrote:
>>
>>> You can find a first draft of the STAP protocol here:
>>> http://personalpages.manchester.ac.uk/staff/s.dalla/astrogrid/strap.html
>>>
>>> best wishes,
>>> Silvia
>
> ------------------------------------
> Silvia Dalla
> School of Physics and Astronomy
> University of Manchester
> PO Box 88
> Manchester M60 1QD
> UK
>
> Tel +44-161-306 8705
> Fax +44-161-306 3941
> ------------------------------------
>