Scope of registry

[Tony Linde]

Small point Clive: registry list address is 'registry at ivoa.net' and not
.org.

The point you raise is interesting and is on the border line between the
'minimal required' standards and the 'extensions' each registry might
implement. The ability to query what part of sky a resource (if it is
that type) covers is necessary; I'm not sure we need to standardise how
this is implemented.

> - We need a way to represent the shape of the field-of-view, some are

Agreed. Both in a query to the registry and in the results returned.

> - We need a way to gather the information from the individual archives: it
> may not be possible to do this by robot, it may need a human to get and
> convert the data to some uniform format (XML-based I'd guess).

It should be done by robot but it'll be up to each data centre to make it
available in one of a few standardly accessible ways: eg xml files in set
location, service with specific api.

> - The Registry will be quite a lot larger if it contains this
> information,
> so the design, even if it omits this type of data initially, must be
> suitable to scale to this size in due course.

This is definitely outwith the scope of IVOA standards: it'll be up to
individual projects to determine how to achieve this.

> So I would urge the Registry designers to consider providing this
> fine-grained information from the outset, if at all possible.

Again, there is no single Registry. Each project will implement this
facility in their own way. They need the ability to respond to
fine-grained queries but the project can decide for itself whether to
include this in their implementation of their registry or to farm such
queries out to the individual resources. AstroGrid will be fine-grained
but other projects may decide differently.

Cheers,
Tony.

On Wed, 5 Feb 2003 09:07:57 +0000 (GMT), "Clive Page" <cgp at star.le.ac.uk>
said:
> I've been visiting the NeSC in Edinburgh for the last few days so haven't
> had time to read all the Registry-related emails carefully, so apologise
> if this posting duplicates something already covered.  But most of the
> discussion I've seen is of computer science topics, and not much on
> scientific requirements.
> 
> It seems to me that one of the most valuable things the registry should
> do
> is to tell the astronomer about _all_ resources which potentially have
> information about some point (or small patch) in the sky - this is the
> obvious extensionh of the cone-search which is widely agreed to be a
> priority VO service.   The user wants to specify the name of an object,
> to
> be turned into coordinates by Simbad/NED, or an (RA,DEC) and perhaps a
> small radius, and be told where there are (or may be) useful information.
> In many (most?) cases the user will also restrict the query with a choice
> of waveband (tell me all radio observations for example) or a limit in
> say
> time of observations (all pre-outburst observations of this star).
> 
> For the well-known surveys this presents few problems, but there are lots
> of observatories which have observed the sky piece-meal.  Many of these
> have on-line observing logs.  For example you can search the archives of
> the HST, or Chandra, or XMM-Newton to see whether your bit of sky has
> ever
> been in their field of view.  This is also possible for many ground-based
> telescopes, and I guess all of them before long.  This information is at
> present obtainable only with great difficulty, as the archives are widely
> scattered with very diverse user interfaces.  In principle the Registry
> could make this _much_ easier.  I think we ought to aim to make this a
> practical reality.
> 
> There are some obvious difficulties:
> 
> - We need a way to represent the shape of the field-of-view, some are
> circular, some rectangular, or odd shaped (e.g. HST).  The data modelling
> people have discussed this, but not yet solved it.
> 
> - We need a way to gather the information from the individual archives:
> it
> may not be possible to do this by robot, it may need a human to get and
> convert the data to some uniform format (XML-based I'd guess).
> 
> - The Registry will be quite a lot larger if it contains this
> information,
> so the design, even if it omits this type of data initially, must be
> suitable to scale to this size in due course.
> 
> Although the difficulties of data gathering and implementation are
> non-trivial, I think they are tractable, and that the resulting gain in
> functionality for the astronomer-in-the-street would be considerable.  A
> registry which could provide this hard-to-get information would put the
> VO
> on the map as something actually useful (a lot of astronomers, at least
> in
> the UK, think the VO movement prettyn much a waste of time and money).
> So I would urge the Registry designers to consider providing this
> fine-grained information from the outset, if at all possible.
> 
> 
> -- 
> Clive Page,
> Dept of Physics & Astronomy,
> University of Leicester,    Tel +44 116 252 3551
> Leicester, LE1 7RH,  U.K.   Fax +44 116 252 3311
> 
> 
__
Tony Linde                       Phone:  +44 (0)116 223 1292
AstroGrid Project Manager        Fax:    +44 (0)116 252 3311
Dept of Physics & Astronomy      Mobile: +44 (0)7753 603356
University of Leicester          Email:  ael at star.le.ac.uk
Leicester, UK   LE1 7RH          Web:    http://www.astrogrid.org

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