W3C home > Mailing lists > Public > public-rdf-wg@w3.org > December 2013

RE: RDF 1.1: "Some properties may change over time." (ISSUE-178)

From: Markus Lanthaler <markus.lanthaler@gmx.net>
Date: Wed, 11 Dec 2013 19:34:36 +0100
To: "'Thomas Baker'" <tom@tombaker.org>, "'Pat Hayes'" <phayes@ihmc.us>
Cc: "'RDF Working Group'" <public-rdf-wg@w3.org>
Message-ID: <013601cef69f$a6478120$f2d68360$@lanthaler@gmx.net>
On Wednesday, December 11, 2013 7:18 AM, Thomas Baker wrote:
> On Tue, Dec 10, 2013 at 11:29:00PM -0600, Pat Hayes wrote:
> > > Works for me. We could perhaps make it even simpler by just saying
> > >
> > >   A relationship that holds between two resources at one time may
> > >   not hold at another time.
> 
> Pat's answer (below) is certainly the more interesting.  However, the
> simple bulleted list at [1] is not a good place to first raise such a
> subtle issue. If Pat's judgement amounts to weak assent, I'd vote +0.5
> for the "least bad" variant above.

OK, I went ahead and made the change. Tom, Pat, could you please tell me
whether you can live with this so that we can close ISSUE-178?


Thanks,
Markus


 
> [1] https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-
> concepts/index.html#change-over-time
> 
> > This last one is the least bad of the lot. But none of them are
> correct.
> > There is a basic issue here. Just like sets, relations cannot really
> change
> > with time. At least, not when they are described using a normal logic
> (they
> > can in a tense logic). What can happen is that something that we
> might
> > casually or carelessly describe as a binary relation is in fact a
> three-way
> > relation with time as its third argument. Now of course [ R(a, b) at
> T ] or
> > R(a, b, T) pretty much mean the same thing and in English we don't
> even have
> > a way to distinguish them; but being all logical and strict about it,
> the
> > three-argument way of talking is more accurate precisely because it
> makes it
> > clear that the *actual relation* does not change, which makes sense
> because
> > relations (speaking now formally and mathematically proper), like
> sets, just
> > aren't the kind of thing that can possibly change. (If this reminds
> y'all of
> > the problems we had with talking about RDF graphs being updated or
> modified,
> > yes it is exactly the same issue.) We could have made RDF into a
> tensed
> > logic, in which all assertions are made at a time, and things like a
> triple
> > being true AT a time would make literal sense; but we didn't. So
> right now,
> > and probably for the forseeable future, the idea of a relation
> changing -
> > holding at one time but not at another time - does not make sense
> according
> > to the RDF conceptual model, so temporal variation like this has to
> be
> > modeled in the same way we would model a three-place relation in RDF.
> >
> > We might say something like this:
> >
> > Some relations have an extra time parameter or are time-dependent.
> Such a
> > relationship that holds between two resources at one time might not
> hold at
> > another time. To describe this in RDF we have to treat the time as an
> extra
> > argument or parameter to the binary relation.
> 
> --
> Tom Baker <tom@tombaker.org>


--
Markus Lanthaler
@markuslanthaler
Received on Wednesday, 11 December 2013 18:35:12 UTC

This archive was generated by hypermail 2.3.1 : Wednesday, 11 December 2013 18:35:13 UTC