VODataService becoming WD, then PR

[Paul Harrison]

On 2008-11 -17, at 06:10, Ray Plante wrote:

> Dear RWG,
>
> The VODataService specification document can now, we believe,  be  
> considered complete and is available from the VODataService twiki page
> (http://www.ivoa.net/cgi-bin/twiki/bin/view/IVOA/VODataService).   
> After finishing a last final reread, I will be posting it as an  
> official Working Draft.  Soon after that, it will be promoted to a  
> PR, and the official RFC will begin.
>
> Because of the rapid turnaound from Working Draft to Proposed  
> Recommendation, I urge co-authors, registry providers and the other  
> interested parties to look it over prior to PR.
>
> thanks,
> Ray Plante
> Regristry Working Group chair
>
>


Hi,

I have one immediate issue with the latest version of the  
VODataService schema/specification. I think that the table description  
should contain an explicit definition of how to specify foreign keys  
that define the relations between tables - these relations are, after  
all, fundamental to the way that the relational databases function,  
and it is impossible to do a multi-table query without this  
information. Whilst I can see that the <relationalJoin> definition was  
rather clumsy, I think that it is possible to come up with something  
much simpler - e.g an optional fkey attribute on a TableParam that  
points to the primary key by using the "table.column" syntax for the  
attribute value.

A human might be able to work out what the foreign keys are by reading  
the descriptions of each TableParam, but a machine could not, and even  
for a human this is sometimes difficult for large schema - you only  
need to look at Sloan http://cas.sdss.org/astrodr7/en/help/docs/realquery.asp 
  to see how often joins are used in useful queries on real databases.

Cheers,
	Paul.

Dr. Paul Harrison
JBCA, Manchester University
http://www.manchester.ac.uk/jodrellbank