W3C home > Mailing lists > Public > public-rdf-wg@w3.org > April 2012

blank nodes as graph labels

From: Sandro Hawke <sandro@w3.org>
Date: Fri, 27 Apr 2012 15:18:49 -0400
To: Andy Seaborne <andy.seaborne@epimorphics.com>
Cc: public-rdf-wg@w3.org
Message-ID: <1335554329.9663.740.camel@waldron>
On Fri, 2012-04-27 at 19:54 +0100, Andy Seaborne wrote:
> >     Comments: I believe this definition is formally equivalent to the
> >     SPARQL definitions and the one in our draft, except (1) some minor
> >     terminology, (2) allowing blank nodes as graph labels, and (3)
> >     allowing blank nodes to be shared between the graphs.
> 
> So why write a new definition?  

Well, several people have said they couldn't see, formally, how to share
blank nodes between graphs.   So I tried to address that.

> All this does is mean that W3C has two 
> definitions of the same thing.

My purpose here was to make very clear, among us, what we're talking
about.   I'm not proposing this as the actual spec language.

> >     I expect the idea of allowing blank nodes to be used as graph labels
> >     to be controversial, but I think it's important for convenience
> >     and to clarify the semantics in the face of possible dereference
> >     operations.  I understand it presents some issues, including
> >     SPARQL compatibility.  I propose we consider this AT RISK through
> >     CR and see how those issues pan out.
> 
> It is a real shame that this proposal starts by being controversial when 
> there may be much to agree in it.
> 
> "AT RISK" at this stage is signaling an open issue.

Yes.  I hoped by being explicit about the controversy, people could see
past it if they didn't like it.

I included it here because I was trying to make a short but complete
proposal for a design that I believe addresses the (never quite
explicit) requirements of the group.   I think, once people have a
chance to see how the proposal works, with the use cases, they'll agree
that this is a worthwhile feature.

> On the blank nodes,
> 
> http://www.w3.org/2011/rdf-wg/meeting/2012-01-04#Issue__3a__should__2f_must_the_4th_slot_be_an_IRI__3f_
> 
> Can we start where there is most agreement which, as I understand it, is 
> IRIs for labels?
> 
> It is then up to those who want bNode for labels to persuade everyone else.
> 
> Let's take a strawpoll.

Sure, after we understand the proposal, and people have a chance to
understand the pros and cons.   In particular: if you're strictly
followintg the Linked Data princples, it's not clear to me how you refer
to an RDF Graph in a dataset, unless you use a blank node.  Do you want
to tell people to use 303-see-other URIs for that?  That seems like an
awful lot (a prohibitive amount) of work for publishers.

       -- Sandro
Received on Friday, 27 April 2012 19:19:01 UTC

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