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Re: Blank Nodes and SPARQL

From: Dan Connolly <connolly@w3.org>
Date: Mon, 11 Jul 2005 13:46:46 -0500
To: kendall@monkeyfist.com
Cc: DAWG Mailing List <public-rdf-dawg@w3.org>, Ron Alford <ronwalf@umd.edu>, "Seaborne, Andy" <andy.seaborne@hp.com>, Eric Prud'hommeaux <eric@w3.org>, public-rdf-dawg-comments@w3.org, Amy Alford <aloomis@glue.umd.edu>
Message-Id: <1121107607.10719.269.camel@localhost>

On Mon, 2005-07-11 at 14:25 -0400, Kendall Clark wrote:
> On Mon, Jul 11, 2005 at 01:18:54PM -0500, Dan Connolly wrote:
> 
> > > Thinking about it a little more, it does seem to change the semantics of
> > > every graph that gets rewritten in that way.
> > 
> > The _!:... mechanism has the same effect, no? In the context in
> > which it's used, it works logically like a URI; i.e. it matches
> > the way URIs match.
> 
> I don't believe so. As Ron says in another message, OWL DL says some things
> (i.e. restrictions) have to be anonymous. _!:foo is still anonymous, while a
> URI isn't.

It's not at all clear to me that _!:foo is anonymous.

In the strict sense that's most relevant, the OWL DL spec doesn't
say whether _!:foo is anonymous or not. It's a new sort of term.

In the requirement we discussed, "it must be possible for a client
to refer to a bnode provided by a server", the word "refer"
suggests that it works like a name.


> So they may be, from some point of view, equivalent, but they have different
> effects, one of which is unacceptable IMO.
> 
> > > 1. It make sense (which is a good thing)
> > 
> > I accept that as your position; I don't share it.
> 
> Care to say why you claim that it doesn't make sense?

I don't understand the proposal. I don't understand how
to relate it to what I know about logic and query languages
(nor our charter, nor web architecture).
These _!:foo things look like logical constants, to me;
i.e. like URIs. But you say they're different. I don't
understand how, except that the scope of _!:foo is
private to a conversation between a client and a server
(which seems to break webarch rule #1
 http://www.w3.org/TR/webarch/#pr-use-uris ).

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Monday, 11 July 2005 18:46:52 GMT

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