IVOA Identifiers Working Draft

[Tony Linde]

> There is also the separate but related question I posed:  Can an IVOA 
> identifier exist for a resource that is not registered 
> anywhere?  If so, 
> what are the constraints (i.e. "as > long as ...")?

Not really since there is no way the registry can know not to create a
ResourceId that conflicts with it.

> Associating Sa.CXO with a data collection's ShortName is not 
> a good idea, 
> because there is no guarantee that it is unique and will consistantly 
> refer to the same data collection.  This is exactly the role of an 
> identifier: to be a unique reference.  

It isn't unique but could be used to get a list of data collections which,
if it is >1 in length would need human intervention.

Not ideal but where is the list of associations between Sa.CXO and the
unique identifier held?

Cheers,
Tony. 

> -----Original Message-----
> From: owner-registry at eso.org [mailto:owner-registry at eso.org] 
> On Behalf Of Ray Plante
> Sent: 12 September 2003 19:33
> To: registry at ivoa.net
> Cc: 'Arnold Rots'
> Subject: RE: IVOA Identifiers Working Draft
> 
> 
> Hi Tony,
> 
> On Fri, 12 Sep 2003, Tony Linde wrote:
> > Referring to my previous email, Sa.CXO is a data collection and 
> > Sa.CXO/2900 is a dataset.
> 
> I have pressed the question as to the role of the first field (e.g. 
> "Sa.CXO").  The answer from Arnold and Tom (correct me if I'm 
> wrong) is 
> that this field is simply to establish a namespace.  Choosing 
> the data 
> collection (or more precisely, the facility from which the data 
> originated) is a convenient way of dividing into namespaces.  
> It plays no 
> other role in the resolving of the identifier.  Thus, it 
> corresponds to 
> our AuthorityID.
> 
> > To resolve Sa.CXO/2900, ADS would look up Sa.CXO in a registry 
> > (assuming Sa.CXO is a ShortName, perhaps?) to get the identifier of 
> > the data collection and would then use that identifier to find sky 
> > services which served that data.
> 
> Associating Sa.CXO with a data collection's ShortName is not 
> a good idea, 
> because there is no guarantee that it is unique and will consistantly 
> refer to the same data collection.  This is exactly the role of an 
> identifier: to be a unique reference.  
> 
> I'm confident that if we can resolve an ADEC identifier to a data 
> collection registered in an IVOA registry, we can 
> transparently return a 
> service (or web page or other URL) for retrieving it.  The 
> open questions 
> are: how do we do that?  should we bother?  
> 
> There is also the separate but related question I posed:  Can an IVOA 
> identifier exist for a resource that is not registered 
> anywhere?  If so, 
> what are the constraints (i.e. "as > long as ...")?
> 
> cheers,
> Ray
>