Error column in VOResource

[Ray Plante]

On Tue, 18 May 2004, Martin Hill wrote:
> Would it be a good idea to include a reference to the associated error 
> column in a column's description?  eg:
> 
> <Column>
>       <vr:Name>FREQ</vr:Name>
>       <vr:Description>Frequency at center of the image 
> wavehand</vr:Description>
>       <DataType>float</DataType>
>       <Unit>Hz</Unit>
>       <ErrorColumn>FREQ_ERR</ErrorColumn>
> </Column>

There is a caution to be made about metadata creep.  The more we put in, 
the more that doesn't get used, the heavier and more complicated to schema 
to understand.  

An important question is, do you see "ErrorColumn" being useful for 
choosing/locating a resource?  (as opposed to querying the table itself.)

Cone Search and SIA both define a metadata query that returns a VOTable 
header.  This would presumably contain this information if it exists 
anywhere.  SkyNode is working on an analagous operation to get this 
information.  

I'm also concerned about our re-inventing the metadata that comes with a 
VOTable.  In previous versions of the schemas, I suggested importing parts 
of the VOTable schema to describe tables within a VOResource; that way you 
get all this richness for free.  Plus, we don't have 2 different ways of 
expressing the same thing.  The only reason I can think of for not doing 
this is that VOTable is somehow not general enough.  

> Also, a rather naive question: I had originally thought that column 
> descriptions were part of the VOResource document, but they don't seem 
> to be there - they seem to be in a VODataService schema.  Have I got 
> that right?  

Yes, since this applies only to tabular data and data services, 
VODataService seems the most appropriate place to put it.  More 
importantly, table descriptions lie at the more unstable end of our schema 
development (as illustrated by this email ;-) so it's best not to have it 
in the core.  

> If so, could we add this to the VOResource page at 
> http://www.ivoa.net/xml/VOResource/ ?

Exactly what do you wish to see on this page?  

Note that all schemas are listed at http://www.ivoa.net/xml/.  Also note 
that http://www.ivoa.net/xml/ is not maintained by the Registry working 
group but by the document coordinator.  Because of the chore of 
maintaining the documents themselves, the presentation is kept pretty 
plain to all automated maintanence.  

cheers,
Ray