- From: Luc Moreau <L.Moreau@ecs.soton.ac.uk>
- Date: Thu, 28 Jul 2011 15:14:43 +0100
- To: public-prov-wg@w3.org
- Message-ID: <EMEW3|7434b6ed53f368e4723d8bf7edb7e4cbn6RFEk08L.Moreau|ecs.soton.ac.uk|4E316ED3>
Yes, Stephen, that seems to be the consequence of this definition. Is it the property we want? Luc On 07/28/2011 03:02 PM, Cresswell, Stephen wrote: > > Paolo, > > The "holds over the temporal intersection" clause is already there in > the definition of IVPof. I am questioning the transitivity of the > relation even with this clause. I think that inference of IVPof using > transitivity from two IVPof assertions is only valid if all three bobs > involved have mutually overlapping intervals (i.e. X must overlap Z in > my example), and it is this condition which is not captured. > > Stephen Cresswell > > Tel: +44 (0) 01603 69 6926 > > Web: www.tso.co.uk <http://www.tso.co.uk/> > > ------------------------------------------------------------------------ > > *From:* Paolo Missier [mailto:Paolo.Missier@ncl.ac.uk] > *Sent:* 28 July 2011 14:29 > *To:* Cresswell, Stephen > *Cc:* public-prov-wg@w3.org > *Subject:* Re: PROV-ISSUE-45: isDerivedFrom and IVPof are transitive. > [Conceptual Model] > > Stephen, > > your observation is correct, of course, and it does make the IVP-of > relation look not well-behaved, but that's because the temporal > interval that defines Bobs validity explicitly, has remained "hidden" > in the def. of IVP-of relation, while it should have been made > explicit there, as well. > So if you add your sentence "B IPVof A is defined to only hold over > the temporal intersection of A and B" to the def. of IVP-of (as we > should have done as it makes no sense to establish a relation between > two Bobs, one of which is out of scope), then over this restricted > interval the relation /is/ transitive, right? > What I mean is that the problem is not that IVP-of is not transitive, > but that in the def. we omitted to qualify the scope within which the > relation itself holds. > > Regarding better-behaved relations, personally (and bear in mind this > is not /my/ def.) I rather like the general case in which > - the set of attributes overlap (with no strict set containment > requirement) > - the temporal scopes overlap (with no strict interval containment > requirement) > as these conditions lead, within a possibly restricted scope, to an > equivalence relation. That said, whether this is still practically > useful is a separate issue... > > -Paolo > > On 7/28/11 1:13 PM, Cresswell, Stephen wrote: > > Paolo, > > I don't see how IVPof can be usefully considered transitive in its > current definition, as I think it would be possible for some > transitively-derived IVPof relations to be valid only over empty time > intervals. This is because B IPVof A is defined to only hold over the > temporal intersection of A and B, but the relation of having non-empty > temporal intersection is itself not transitive. > > For example, we can have three time intervals X, Y, Z such that X > overlaps Y, Y overlaps Z, but X is disjoint from Z. > > Then if we have bobs Bx, By, Bz which hold over the respective time > intervals, and we asserted > > Bx IVPof By > > By IVPof Bz > > ... then transitivity would allow us to derive > > Bx IVPof Bz > > ... but that is dubious because it would hold only over the temporal > intersection of X and Z, which is empty. > > I was hoping that the definition of B IVPof A would turn out to > require that the time interval of B was contained in the time interval > of A. I think that would be a simpler and better-behaved relation, > which should be glorified with a name, even it's not "IVPof". > > Stephen Cresswell > > Tel: +44 (0) 01603 69 6926 > > Web: www.tso.co.uk <http://www.tso.co.uk/> > > ------------------------------------------------------------------------ > > *From:* public-prov-wg-request@w3.org > <mailto:public-prov-wg-request@w3.org> > [mailto:public-prov-wg-request@w3.org] *On Behalf Of *Paolo Missier > *Sent:* 25 July 2011 12:30 > *To:* public-prov-wg@w3.org <mailto:public-prov-wg@w3.org> > *Subject:* Re: PROV-ISSUE-45: isDerivedFrom and IVPof are transitive. > [Conceptual Model] > > Khalid > > I don't think we have ever agreed on that, but I should really check > the voting history. The latest definition of IVP-of (or complement-of) > is sufficiently precise (i.e., algorithmic) that transitivity follows, > but derivation is purely asserted and as such there is no ground to > say that it is transitive -- unless we say axiomatically that it > should be. > > -Paolo > > > > > > PROV-ISSUE-45: isDerivedFrom and IVPof are transitive. [Conceptual Model] > > http://www.w3.org/2011/prov/track/issues/45 > > Raised by: Khalid Belhajjame > On product: Conceptual Model > > > If we agree that "isDerivedFrom" and "IVPof" are transitive, then I would suggest that this should be specified in the model working draft. > > khalid > > > > ________________________________________________________________________ > This e-mail has been scanned for all viruses by Star. The > service is powered by MessageLabs. For more information on a proactive > anti-virus service working around the clock, around the globe, visit: > http://www.star.net.uk > ________________________________________________________________________ > > *********************************************************************************************** > > This email, including any attachment, is confidential and may be > legally privileged. If you are not the intended recipient or if you > have received this email in error, please inform the sender > immediately by reply and delete all copies from your system. Do not > retain, copy, disclose, distribute or otherwise use any of its contents. > > Whilst we have taken reasonable precautions to ensure that this email > has been swept for computer viruses, we cannot guarantee that this > email does not contain such material and we therefore advise you to > carry out your own virus checks. We do not accept liability for any > damage or losses sustained as a result of such material. > > Please note that incoming and outgoing email communications passing > through our IT systems may be monitored and/or intercepted by us > solely to determine whether the content is business related and > compliant with company standards. > > *********************************************************************************************** > > The Stationery Office Limited is registered in England No. 3049649 at > 10 Eastbourne Terrace, London, W2 6LG > > > > > -- > ----------- ~oo~ -------------- > Paolo Missier -Paolo.Missier@newcastle.ac.uk <mailto:Paolo.Missier@newcastle.ac.uk>,pmissier@acm.org <mailto:pmissier@acm.org> > School of Computing Science,Newcastle University,UK > http://www.cs.ncl.ac.uk/people/Paolo.Missier > > > ________________________________________________________________________ > This e-mail has been scanned for all viruses by Star. The > service is powered by MessageLabs. For more information on a proactive > anti-virus service working around the clock, around the globe, visit: > http://www.star.net.uk > ________________________________________________________________________ > -- Professor Luc Moreau Electronics and Computer Science tel: +44 23 8059 4487 University of Southampton fax: +44 23 8059 2865 Southampton SO17 1BJ email: l.moreau@ecs.soton.ac.uk United Kingdom http://www.ecs.soton.ac.uk/~lavm
Received on Thursday, 28 July 2011 14:15:34 UTC