Dear All, I am trying to understand how one can infer the current custody / ownership / location of a Physical Thing / Object.
Let's assume that there has been a E10 Transfer of Custody / E8 Acquisition / E9 Move to an Actor or Place y. If there was no later event at all, it is inferred in the scope notes of P50 has current keeper / P52 has current owner / P55 has current location that y is, in fact, the current keeper / owner / location. For example, the scope note of "P52 has current owner" says: "This property is a shortcut for the more detailed path from E18 Physical Thing through P24i changed ownership through, E8 Acquisition, P22 transferred title to to E39 Actor, if and only if this acquisition event is the most recent." There is a stronger-sounding but actually weaker requirement that there was no later event that included a "P28 custody surrendered by / P23 transferred title from / P27 moved from" y. The owner / location scope notes use the stronger requirement, the keeper scope note uses the weaker requirement. It would be good to explain in the respective scope notes the reasoning behind this difference. The FOL encodes the weaker requirement in all three cases. I assume the discrepancy between scope notes and FOL is an oversight. (This was actually my starting point.) The scope notes not only say "if" but "if and only if". Is there a way to encode the "only if" part in FOL? This seems to be quite tricky. For example, if there were three Moves: 1. from somewhere to A, 2. from A to B, 3. from B back to A, then one can infer that A is the current location, but only Move 3 (and not Move 1) is actually the long form of the shortcut "P55 has current location". On the other hand, it does not follow from Move 1 and 2 that A is not the current location. Should we worry about negative statements and incomplete knowledge in our knowledge base? Or do we assume here that if there has been such an event, then the knowledge base knows about it? (Or equivalently, if the knowledge base does not know of any such event, then there was indeed none?) Of course one can infer e.g. the current location based on a possibly incomplete list of Moves in a given knowledge base, but whose opinion would it represent? Can one still claim that the inferred statement is the opinion of the knowledge base maintainers? In particular, what happens if an object disappears or gets destroyed? One may infer the last keeper / owner / location before the destruction, but both the scope notes and the FOL will happily argue that the destroyed object nonetheless has a current owner / keeper / location. Perhaps the destruction implies an implicit Transfer Of Custody where the custody has been surrendered, but there is probably no implicit Acquisition or Move. E64 End of Existence and E6 Destruction offer no concrete help, although E64 says: "It may be used for temporal reasoning about things … ceasing to exist". I assume this has already been discussed somewhere, but the discussion didn't find its way into the scope notes. Best, Wolfgang _______________________________________________ Crm-sig mailing list Crm-sig@ics.forth.gr http://lists.ics.forth.gr/mailman/listinfo/crm-sig
