[Mulgara-dev] CRITICAL: Bug fix to Backup operation (off-topic)

[Alex Hall]

Paul Gearon wrote:
> 
> On Thu, Mar 27, 2008 at 3:44 PM, Alex Hall <alexhall at revelytix.com 
> <mailto:alexhall at revelytix.com>> wrote:
> 
>     As far as I can recall, the main difficulty in maintaining a reference
>     to a blank node across transactions lies in the fact that the underlying
>     gNode may have been released and reallocated in the meantime.
>     Therefore, even though I believe the Connection API allows for a blank
>     node to be used in a query constraint (and possibly other places), doing
>     so is not guaranteed to give the results you may have expected.
>     Certainly the TQL query grammar does not support a blank node in a query
>     constraint.
> 
>     The news that gNodes won't be reused in the new string pool
>     implementation seems to suggest that the identity of a blank node
>     reference will remain intact across the lifetime of the database.  If
>     this is indeed the case, then would we be able to explicitly support the
>     use of blank nodes in queries?  That would be a most welcome
>     enhancement.
> 
> 
> Yes. It will probably give the RDF folks apoplexy, but this will be fine.

The way I see it, as long as we can uniquely and without risk of 
ambiguity identify an anonymous node, there's no reason not to treat it 
like any other resource.  I can think of plenty of cases where this 
might be useful.  For instance, suppose you have an RDF visualization 
application and there is an anonymous resource that you want to find 
more information about -- perhaps you want to find all incoming and 
outgoing relationships involving that node.  It doesn't make much sense 
to me to disallow this operation just because the author of the graph 
didn't give that resource an identifier.  But then we're getting into a 
philosophical discussion...

-Alex