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RE: Unbound vars as blank nodes

From: Geoff Chappell <geoff@sover.net>
Date: Wed, 23 Mar 2005 11:03:36 -0500
To: <andy.seaborne@hp.com>
Cc: <public-rdf-dawg-comments@w3.org>
Message-ID: <002b01c52fc1$df8535d0$6401a8c0@gsclaptop>



> -----Original Message-----
> From: Seaborne, Andy [mailto:andy.seaborne@hp.com]
> Sent: Wednesday, March 23, 2005 9:30 AM
> To: Geoff Chappell
> Cc: public-rdf-dawg-comments@w3.org
> Subject: Re: Unbound vars as blank nodes
> 
> 
> 
> Geoff Chappell wrote:
> >
> >
> >>-----Original Message-----
> >>From: Arjohn Kampman [mailto:arjohn.kampman@aduna.biz]
> >>Sent: Wednesday, March 23, 2005 5:52 AM
> >>To: Geoff Chappell
> >>Cc: public-rdf-dawg-comments@w3.org
> >>Subject: Re: Unbound vars as blank nodes
> >>
> >
[...]

> > That's not to say NULLs won't work. I think a perfectly workable
> solution is
> > to require that all vars mentioned in a pattern element are bound to
> > something by that pattern element -- if not to an actual value, then to
> NULL
> > -- and that NULL != NULL. IMHO that would resolve the current execution
> > ordering mess (I've heard statements to the contrary but I've never seen
> a
> > counter example).

My apologies... I guess I stand corrected :-)

I see now that:

>    ?x foaf:name  ?name .
>    ?y foaf:mbox ?mbox .
>    OPTIONAL { ?x foaf:mbox ?mbox } .

returns more solutions than I'd claimed in our earlier conversation. (I wish
I'd kept my rdfql test queries so I could see where my error was.)

I won't bother responding to the rest until I reset and wrap my head around
this :-)

Geoff 
Received on Wednesday, 23 March 2005 16:05:09 GMT

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