W3C home > Mailing lists > Public > public-linked-json@w3.org > July 2013

RE: Input needed from RDF group on JSON-LD skolemization

From: Markus Lanthaler <markus.lanthaler@gmx.net>
Date: Thu, 4 Jul 2013 10:16:27 +0200
To: <public-linked-json@w3.org>
Message-ID: <050301ce788e$c93e3730$5bbaa590$@lanthaler@gmx.net>
On Thursday, July 04, 2013 3:54 AM, David Booth wrote:
> >> Regarding stability, AFAICT relative IRIs would be nearly as stable as
> >> any versioned IRI: the IRI may change if the author decides to version
> >> it, but aside from that it is exactly the same every time the data is
> >> generated, even if other data elements are added, etc.  That is far
> >
> > I completely disagree. While technically you are right, the whole point
of
> > using a bnode is to convey it is in fact *not stable* and is not
intended
> > to be.
> 
> Again, you may think of blank nodes that way if you wish, but that is
> not why they were invented.

Just out of curiosity, why have they then been invented if not provide a way
to express some facts about an "entity" that is unknown?


> > The point is that I don't want them to be stable. I explicitly want to
> > prevent that people start to rely on them.
> 
> I suppose that would make sense if your goal is to annoy downstream
> consumers of your data, but that's rather anti-social.   Making it hard
> for others to refer to resources mentioned in your data is widely
> viewed
> as a *negative* -- not a positive -- and it goes against the philosophy
> of the web.

That might be true.. but exactly the same applies to bnode subjects and
objects. Arguably even more so to subjects. So why do you think predicates
are so special?


> > OK, so what if we would add a "generalizedRDF" flag to the toRDF
algorithm
> > which, when set to false would filter all quads where a bnode is in
> > predicate position? I would prefer the default value to be set to true
but
> > could, if there's a good argument, also live with a false.
> >
> > Would that address your concerns?
> 
> Well, no.  An option for extended RDF would be fine (defaulting to
> standard RDF), but discarding triples would not be fine, because it
> would involve unnecessary information loss.  That would bring us back to
> figuring out how to avoid that information loss.  Skolemization would be
> one way to do it, but the use of relative URIs seems like a better
> option because it is so much simpler and it gives the additional
> benefits (which I understand you do not see as benefits) of more stable
> identifiers that could eventually be made dereferenceable.

You can't have a syntax which sometimes allows bnode predicates and
sometimes doesn't. The only option in that case is to raise an error when
converting to RDF saying that information may be lost because some generated
triples contain bnode predicates. That would be acceptable for me but I fear
it won't satisfy you either.



--
Markus Lanthaler
@markuslanthaler
Received on Thursday, 4 July 2013 08:16:59 UTC

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