W3C home > Mailing lists > Public > public-rdf-wg@w3.org > March 2011

Re: A modest proposal concerning blank nodes.

From: Sandro Hawke <sandro@w3.org>
Date: Wed, 02 Mar 2011 21:16:59 -0500
To: Gavin Carothers <gavin@topquadrant.com>
Cc: Pat Hayes <phayes@ihmc.us>, RDF-WG WG <public-rdf-wg@w3.org>
Message-ID: <1299118619.2169.244.camel@waldron>
On Wed, 2011-03-02 at 16:04 -0800, Gavin Carothers wrote:
> On Wed, Mar 2, 2011 at 2:47 PM, Pat Hayes <phayes@ihmc.us> wrote:
> > Ahem.
> >
> > Thinking about this (below) and reading recent threads, I think I agree. Blank nodes are more trouble than they are worth. Lets get rid of them.
> 
> Quick run around the office here to this idea led to a rather simple
> answer. Such a change would likely be out of charter. I don't think
> the rest of the argument matters in addressing wither or not removing
> Blank nodes is in charter, and I'm going to avoid disagreeing or
> agreeing.

I agree it would be out of scope to just "get rid of" blank nodes, but
as I read the charter, the WG has considerable latitude to "weakly
deprecate" things.  If we really all agree people should not be using
blank nodes, then I think we could weakly deprecate them.   That would
mean they would stay in the specs, and RDF software would still have to
handle them, but content creators (and creators of systems producing
RDF content) would be advised against using them.   

I think, by the end of Pat's modest proposal, he'd come full circle to
saying he was really just going to change blank node semantics, not
really get rid of them.   As I read it, that tweaking of the semantics
is explicitly out-of-scope in the charter.  However, Pat argues that
he'd be changing them to what people actually implement; I'm not sure
where we are on the scope if everyone actually agrees on that claim.
Maybe we can at least defer that debate until we've addressed our
more-pressing deliverables?

There's obviously a lot more to say about blank nodes, but given my
current understanding, I think the next version of the specs should at
least explain the costs of using blank nodes, and perhaps counsel in
favor of various alternatives.   Maybe that's just some text in the
tutorial; maybe it's something stronger than that.   For some thoughts
on that see [1].

FWIW, as much as I love them [2], I'm not at all sure tag: URIs are
better than blank nodes, especially when machine-generated.  Pat says
systems would have to do the naming "in some systematic way", and my gut
feeling is that's equivalently hard to working with blank nodes.  In
practice, it might be even worse, because if people did it badly they
could easily produce vast numbers of tag: URIs for the same thing.
Perhaps I'm misunderstanding that part of the proposal; I don't really
understand how RDF lists would be handled, for instance.

    -- Sandro

[1]
http://richard.cyganiak.de/blog/2011/03/blank-nodes-considered-harmful/
[2] http://www.w3.org/2001/02/tann/
Received on Thursday, 3 March 2011 02:17:08 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 17:04:03 UTC