Since my HW is mentioned. I tried to explain the change, P7(x,y) ∧ P89(y,z) ⇒ P7(x,z), seen form the point of view of practical applications. Martin argue correctly from a principle point of view.
Time reasoning is similar, on the the two dimensional time line. A historian or an archaeologist will try to date an event A from the intersection of the timespan of other events during which A must have happened, see https://proceedings.caaconference.org/paper/17_holmen_ore_caa2009/ for a pedagogical, fictitious example. That the black plague in Norway happened in the 14th c. can of course be deduced form the usual estimate 1348-1350, but is usually not used in historical reasoning. Best, Christian-Emil ________________________________ From: Crm-sig <[email protected]> on behalf of Martin Doerr via Crm-sig <[email protected]> Sent: 20 October 2022 20:56 To: [email protected] Subject: Re: [Crm-sig] Is P7(x,y) ∧ P89(y,z) ⇒ P7(x,z) still regarded as true? Dear Wolfgang, I regard that the statement P7(x,y) ∧ P89(y,z) ⇒ P7(x,z) was never true, and following the decision of the last SIG it does no more appear. The oral explanation in the SIG that is causes a useless recursion through the world was just an indication that it was nonsensical from the beginning. In my understanding, it was a confusion taking an inverse shortcut for a shortcut. In my understanding, and actual scholarly practice, P7 expresses a reasonable, NOT arbitrarily large, outer approximation of the place where something happened. The narrower the better. Indeed, "we now say that we need to have an explicit statement that x was within a place y and regard only the statements P7(x,z) to be true or inferrable for all z between the spatial projection and y" That is in the new FOL, isn't it? Indeed, "If I have a statement in my information system that, lacking more precise information, a period such as the move of an object took place somewhere in Europe, is P7 then automatically true for all places between the spatial projection of the move and Europe but my information system couldn't actually infer any additional P7 statement because it doesn't know where the declarative place of the spatial projection is" We should be aware that "approximation" has no equivalent in FOL. It has a quality, which can be formalized by metrics. If you have some background knowledge in topology, you may be familiar with the respective concepts. Automatically, the intersection of all yi, i=1...n of P7(x,yi) constitutes the best approximation. Best, Martin On 10/20/2022 3:12 PM, Wolfgang Schmidle via Crm-sig wrote: Sorry, second attempt: According to Christian-Emil's homework for issue 606, the reason to avoid the statement P7(x,y) ∧ P89(y,z) ⇒ P7(x,z) was that it might create problems in hypothetical information systems that are clever enough to traverse the graph created by all P89 statements but not clever enough to not fill themselves up with large amounts of deduced P7 statements. If we accept this argument, do we still regard P7(x,y) ∧ P89(y,z) ⇒ P7(x,z) as true based on the semantics of P7 and P89? Or do we now say that we need to have an explicit statement that x was within a place y and regard only the statements P7(x,z) to be true or inferrable for all z between the spatial projection and y? If the latter: If I have a statement in my information system that, lacking more precise information, a period such as the move of an object took place somewhere in Europe, is P7 then automatically true for all places between the spatial projection of the move and Europe but my information system couldn't actually infer any additional P7 statement because it doesn't know where the declarative place of the spatial projection is? Am 20.10.2022 um 13:56 schrieb Wolfgang Schmidle via Crm-sig <[email protected]><mailto:[email protected]>: Quick question: According to Christian-Emil's homework for issue 606, the reason to avoid the statement P7(x,y) ∧ P89(y,z) ⇒ P7(x,z) was that it might create problems in hypothetical information systems that are clever enough to traverse the graph created by all P89 statements but not clever enough to not fill themselves up with large amounts of deduced P7 statements. If we accept this argument, do we still assume that P7(x,y) ∧ P89(y,z) ⇒ P7(x,z) is true based on the semantics of P7 and P89? Or do we now say that we need to have an explicit statement that x was within a place y and regard only the statements P7(x,z) to be inferrable for all z the spatial projection and y? If the latter: If I have a statement in my information system that, lacking more precise information, an object is located (or the move of an object took place) somewhere in Europe, is P7 then automatically true for all places between the spatial projection and Europe but my information system couldn't actually infer any additional P7 statement because it doesn't know where the declarative place of the spatial projection is? Best, Wolfgang _______________________________________________ Crm-sig mailing list [email protected]<mailto:[email protected]> http://lists.ics.forth.gr/mailman/listinfo/crm-sig _______________________________________________ Crm-sig mailing list [email protected]<mailto:[email protected]> http://lists.ics.forth.gr/mailman/listinfo/crm-sig -- ------------------------------------ Dr. Martin Doerr Honorary Head of the Center for Cultural Informatics Information Systems Laboratory Institute of Computer Science Foundation for Research and Technology - Hellas (FORTH) N.Plastira 100, Vassilika Vouton, GR70013 Heraklion,Crete,Greece Vox:+30(2810)391625 Email: [email protected]<mailto:[email protected]> Web-site: http://www.ics.forth.gr/isl
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