URLs?

[Rob Seaman]

Great workshop!  Thanks to everybody who helped make it so.  Will  
write more on this after catching up on my sleep.

On Dec 8, 2005, at 6:15 AM, Norman Gray wrote (to the semantics list):

> The big difference between URIs and URLs is, as we all know, that  
> the former are for labelling concepts, and aren't guaranteed to be  
> dereferencable, much less immediately retrievable.  However a long- 
> established bit of good practice here is to make your URIs  
> retrievable and to provide _something_ useful at the end of it, be  
> it a human-readable description of your namespace, or of your  
> ontology, or whatever you personally mean by the concept thus  
> labelled.

It seems to me that we have never directly discussed the value of  
using URIs instead of URLs as identifiers within VOEvent.  We've  
attempted to adopt the larger IVO standard in this case as in others,  
but while STC, for example, is having to prove its specific worth to  
VOEvent, our packet identifiers have not.

We had a productive session on Wednesday discussing common issues  
related to building interoperable prototypes.  Surely the packet IDs  
will prove central to any such goal.  We also discussed, but chose  
not to reach a conclusion about, how best to support queries against  
a VOEvent "broker's" packet repository.  (One conclusion reached,  
however, is that publishing an event does not automatically imply  
persisting the event.)  Might not one way of doing this  be for a  
particular broker to simply choose URLs as IDs?  Something like:

	<VOEvent id="http://archive.noao.edu/voevent?123456" ...>

Perhaps this is a horrible idea.  After all, we can't ensure that  
archive.noao.edu will persist indefinitely.  On the other hand, the  
requirements for the permanence of VOEvent packets may well be  
significantly shorter than for other archival VO data products.   
Certainly it would be trivial for users to retrieve packets via such  
a mechanism.

I'm not necessarily seeking a change, but I think VOEvent would  
benefit from aggressively challenging this facet of the standard.   
Having survived such a challenge, the utility of IVO identifiers  
within the larger VO might then be further clarified (or just  
possibly, be discarded outright).

Rob