Minutes MWG 2003-09-25

[Tony Linde]

Hi Roy,

I completely agree with all you say - there's a first time for everything :)

Cheers,
Tony. 

> -----Original Message-----
> From: owner-metadata at us-vo.org 
> [mailto:owner-metadata at us-vo.org] On Behalf Of Roy Williams
> Sent: 02 October 2003 22:34
> To: Ray Plante; metadata at us-vo.org
> Cc: registry at ivoa.net
> Subject: Re: Minutes MWG 2003-09-25
> 
> 
> (1) ADQL is semantically similar to SQL, it is something for 
> querying relational databases like star catalogs -- eg "find 
> all rows in the table where alpha > 3". ADQL extends SQL 
> because it has concepts of coverage and proximity.
> 
> (2) Xquery is for querying hierarchical databases (like XML 
> documents). (see
> example* below). Xquery is made for XML (which VOResource 
> is), and there are existing implementations.
> 
> I believe that we are agreed that an SQL-type language is 
> best for relational databases of stars, and that our 
> agreement from Cambridge covers this. However, the registry 
> is different from a star catalog in several ways
> (a) the structure is more complex, with repeated elements (eg 
> authors), and
> (b) the amount of data is much less. In other words, the 
> registry is *metadata*, not *data*. There is not much 
> experience on querying these -- because we do not actually 
> have any significant VO registries yet!
> 
> Querying the registry is not a solved problem (like SQL and 
> star catalogs). There is no benefit in entrenching ourselves 
> in a position. I think we in the IVOA should continue to 
> investigate ways to make client software for VO registries, 
> and hope that by this time next year we will be sufficiently 
> informed to consider a standards process.
> 
> Roy
> 
> --------------------------------
> * Xquery example (approx) -- would select the Messier catalog 
> from the resources in the Caltech registry:
> 
> <query>
> { for $b in document("nvo.caltech.edu/registry.xml")/VOResource
>   where $b/Curation/Creator="Messier" and $b/@date<1800
>   return <resource year="{$b/@date}"> {$b/Curation/Title} 
> </resource> } </query>
> 
> 
> --------
> Caltech Center for Advanced Computing Research 
> roy at cacr.caltech.edu 626 395 3670
>