- From: David Wood <david@3roundstones.com>
- Date: Tue, 17 Dec 2013 18:27:52 -0500
- To: Pat Hayes <phayes@ihmc.us>
- Cc: Markus Lanthaler <markus.lanthaler@gmx.net>, Thomas Baker <tom@tombaker.org>, RDF Working Group <public-rdf-wg@w3.org>
- Message-Id: <90D64186-0B53-402D-8414-B8896FB0DB9B@3roundstones.com>
On Dec 12, 2013, at 04:28, Pat Hayes <phayes@ihmc.us> wrote: > > On Dec 11, 2013, at 10:34 AM, Markus Lanthaler <markus.lanthaler@gmx.net> wrote: > >> 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? > > Yes, I can live with it. Just so I am on record, I’m fine with this too. Thanks, Markus, Pat and Tom. Regards, Dave -- http://about.me/david_wood > > Pat > >> >> >> 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 > > ------------------------------------------------------------ > IHMC (850)434 8903 home > 40 South Alcaniz St. (850)202 4416 office > Pensacola (850)202 4440 fax > FL 32502 (850)291 0667 mobile (preferred) > phayes@ihmc.us http://www.ihmc.us/users/phayes
Attachments
- application/pkcs7-signature attachment: smime.p7s
Received on Tuesday, 17 December 2013 23:28:17 UTC