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Subject: RE: [xdi] More comments on XDI metagraph predicate examples (was: RE: [xdi] Minutes: XDI TC Telecon Thursday 1-2PM PT 2008-12-18)
I agree with Nick - much of this appears to conflate $has metagraph statements with $is$a metagraph statements. But this thread has grown so long (and I'm coming to it so late Friday night) that I'm going to get a good sleep and then send some fresh message RE the questions Giovanni and Bill have raised. 'night, =Drummond > -----Original Message----- > From: Nick Nicholas [mailto:opoudjis@optushome.com.au] > Sent: Friday, January 09, 2009 7:10 PM > To: OASIS - XDI TC > Subject: Re: [xdi] More comments on XDI metagraph predicate examples (was: > RE: [xdi] Minutes: XDI TC Telecon Thursday 1-2PM PT 2008-12-18) > > I'm sorry, but I'm not liking the turn this is taking at all. > > I am still unhappy about the smooshing together of (+a+b)+c and +a(+b > +c). +a/$has/+b+c and +a+b/$has/+c are clearly different predicates. > And an "empty bottle collection" can refer to two different states of > affairs. > > Moreover, clearly +a+b is a distinct entity to +a and +b. +a+b may be > a subclass of +a, or a subclass of +b --- or either, although that's > an outcome I'd hope to avoid. > > To cast +a+b as a constraint rather than as a description of a > distinct entity is misleading. +a+b IMPLIES +a/$has/+b, but +a+b is > not EQUIVALENT TO +a/$has/+b. "Bird wings" is not the constraint > "Birds have wings": it is the entity "bird wings", which presupposes > the statement "birds have wings". > > Given that, (+a+b)+c tells you that +a/$has/+b, and that +a+b/$has/+c. > It tells you absolutely nothing about a relation between either +a or > +b and +c. That's because we don't have an +a+b/$is$a statement > inferred anywhere. > > +bison+female+mammaries > > does not imply > > +bison/$has/+mammaries (male bisons don't) > > nor > > +female/$has/+mammaries (female reptiles don't) > > All you can infer is +bison+female/$has/+mammaries . (In fact, +mammal/ > $a/+bison and +mammal+female/$has/+mammaries, ergo +bison+female/$has/ > +mammaries .) +flyingbird+wings+flightspeed does not mean +flyingbird > +wings and +wings+flightspeed , for the same reason: at most, +wings > +flightspeed only in the context of +flyingbird+wings. But even that > is not guaranteed, because +a+b/$is$a/+a is possible, so you end up > with +a+b and +a+c, not +a+b and +b+c: > > =hector+male > =hector+male+wife > > =hector/$has/+male =hector/$has/+wife not: +wife/$has/+male > > So I question attempts to impose transitivity on properties of +a+b+c. > > As for what follows, p => r and q => r hardly means that p == q. They > don't describe the same state of affairs, so they're not the same > outcome. > > On 10/01/2009, at 12:46 AM, Barnhill, William [USA] wrote: > > > Hi Giovanni, > > > > I think I understand your first question but I think the reversal of > > +a+b+c still works I think. > > > > Paraphrasing what you said (let me know if wrong) as the XRI +a+b+c > > entails either > > (1) +a+b/$has/+c > > or > > (2) +a/$has/+b+c > > or > > (3) both > > > > and the outcomes are different in each case. > > > > It seems to me the outcomes would be the same though, as doesn't > > (1) the XRI +a+b/$has/+c entail the XRI +a/$has/+b//$has/+c > > (2) the XRI +a/$has/+b+c entail the XRI +a/$has/+b//$has/+c > > (3) If we use the following substitutions > > p : +a+b/$has/+c > > q : +a/$has/+b+c > > r : +a/$has/+b//$has/+c > > and from (1) and (2) we know that p entails r, q entails r, then > > p and q -> r, so both XRI's being entailed still entails +a/$has/+b// > > $has/+c > > > > What about the reverse way? > > +a/$has/+b//$has/+c > > a)=> +a+b//$has/+c => +a+b+c > > b)=> +a/$has/+b+c => +a+b+c > > > > I am unsure about entailments above as they involve '//' though and > > need to punt to Drummond: > > Does +a/$has/+b//$has/+c entail +a/$has/+b+c? > > Pretty sure it has to for $has to work as it's being used and have > > it be an inverse functional property. > > > > Also in general can +a/P/Q//R be treated as +a/P/Q/R? > > Not sure on this one. > > > > Thanks, > > =Bill.Barnhill > > > > -----Original Message----- > > From: Giovanni Bartolomeo [mailto:giovanni.bartolomeo@uniroma2.it] > > Sent: Fri 1/9/2009 5:47 AM > > To: Drummond Reed > > Cc: 'Nick Nicholas'; 'OASIS - XDI TC' > > Subject: [xdi] More comments on XDI metagraph predicate examples > > (was: RE: [xdi] Minutes: XDI TC Telecon Thursday 1-2PM PT 2008-12-18) > > > > Hello Drummond, > > > > thank you for your answers; but I fear I've some more concerns.. > > please see my comments below. > > > > Thanks, > > Giovanni > > > > > > > > > > At 09.09 30/12/2008, Drummond Reed wrote: > > > > Giovanni pointed out that Statement 6 in the xdi-rdf-graphing- > > v1 document is > > not consistent with the link contract example found on page > > 33 of the > > xdi-rdf-model-v11 document: > > > > http://www.oasis- > open.org/committees/download.php/29748/xdi-rdf-model-v11.pd > > <http://www.oasis-open.org/committees/download.php/29748/xdi-rdf-model- > v11.pd > > > > > f > > > > In that document, =drummond/$has/+friend$contract results in > > the XRI > > =drummond+friend$contract, but it should be =drummond(+friend > > $contract). > > Drummond agreed this should be changed in the next version. > > > > UPDATE: In his study of the Statement 6 issue identified by > > Markus, Drummond > > subsequently revised the proposed graph structure for > > compound $has > > statements. This eliminates the issue identified by Markus > > and also removes > > the inconsistency with the V11 XDI RDF Model document. V2 of > > the XDI RDF > > Graphing document has been posted at: > > > > > > > > > > > > [giovanni] To further clarify, I also propose to have > > > > (1) =drummond+friend/$has/$contract > > > > instead of > > > > (2) =drummond/$has/+friend$contract > > > > even if they both result in > > > > (3) =drummond+friend$contract > > > > statement (2) seems to me to assert that a subject +friend > > $contract exists regardless the context it is intended to be into > > (=drummond). Statement (1) instead put $contract in the context of > > =drummond+friend and +friend in the context of =drummond. Or maybe > > I'm missing something? > > > > [=Drummond] No, I think you are correct, statement (2) > > implies that there is a XDI subject with the XRI +friend$contract. > > But I think that is implied in all cumulative $has statements. As I > > clarified in the page I just posted ( http://wiki.oasis- > open.org/xdi/XdiOne/RdfGraphModel > > <http://wiki.oasis-open.org/xdi/XdiOne/RdfGraphModel> ), in an XDI > > context, the XRI =drummond+friend$contract infers all of the > > following XDI RDF statements: > > > > (a) =drummond/$has/+friend/ > > (b) =drummond+friend/$has/$contract > > (c) =drummond/$has/+friend$contract > > > > > > > > > > [giovanni] Yes, I see that > > > > +a/$has/+b+c ==> +a+b+c > > +a+b/$has/+c ==> +a+b+c > > > > > > however, if you want to REVERSE these statements, starting from +a+b > > +c, you can infer EITHER (1) +a/$has/+b+c OR (2) +a+b/$has/+c OR (3) > > both. And the outcomes are different in the three different cases. > > In particular, if you have (1) +a/$has/+b+c, this implies that you > > should have also +b/$has/+c. > > But if you have (2), then you should have also +a/$has/+b. > > > > Coming back to the example, from =drummond+friend$contract you may > > infer > > > > (1) > > =drummond/$has/+friend/ > > =drummond+friend/$has/$contract > > > > OR > > > > (2) > > +friend/$has/$contract > > =drummond/$has/+friend$contract > > > > OR (3) > > both. > > > > I think that (1) and (2) are asserting very different things and > > that (1) is what we want to say, whereas (2) is not the same. > > > > > > > > [giovanni] In example #8 (equivalence +x/$is/+y) the arc > > connecting the two circles is labelled with +y, does it have a > > particular meaning? Maybe, for consistency's sake, it is better to > > maintain the graphical convention to name the arc after the > > predicate. Since $is is a symmetric predicate, what do you think > > about the following amendment? > > > > > > > > [=Drummond] The graph you draw is 100% accurate - it is a > > depiction of the full metagraph statement, i.e., of the XDI RDF > > statement +x/$is/+y. The graph I was drawing is a depiction of the > > resulting statement in the XDI RDF graph, which is that the node +x > > has a self-referential arc of type +y. So both are correct, and I > > agree we should show both in the two columns. I'll make a note to > > revise that in the next version. > > > > > > [giovanni] Ok, I see. But in the graph in example #9 > > +x/$has$a/+y > > +x/+y > > the arc +y is used to represent a property belonging to +x (this > > also applies to all meta-graphs depicted in the document). Thus > > wouldn't the picture in example #8 read as: +x has a property +y > > whose value is +x itself: +x/+y/+x ? > > > > BTW I think this is strongly related to another issue which has come > > to my mind. I remember that in the ATI model it was stated that > > addresses refer to ARCs, not to NODEs. This is consistent with some > > OO programming languages like c++ and Java which have the concepts > > of pointers and objects. Pointers are represented through arcs > > pointing to nodes which are objects. Maybe we have a similar issues > > here: XDI addresses might be arcs, not nodes. > > > > > > > > This should address also Markus' question: > > > > [markus] BTW in your terminology, a predicate is not a node in the > > graph, right? So predicates themselves don't have addresses? > > > > What about to amend this > > > > "Every *node* in the XDI RDF graph can be addressed by at least one > > XRI > > representing an XDI address, and every XDI address identifies a > > unique *node* > > in the XDI RDF graph." > > > > into > > > > "Every *ARC* in the XDI RDF graph can be addressed by at least one XRI > > representing an XDI address, and every XDI address identifies a > > unique *ARC* > > in the XDI RDF graph." > > > > (..but maybe I can miss some issues here...)? > > > > > > > > > > <8b72075.jpg><8b720e2.jpg> > > &&& > NON ME TENENT VINCVLA NON ME TENET CLAVIS STETIT PVELLA RVFA TVNICA > Dr Nick Nicholas IT Consultant, Link Affiliates > QVAERO MIHI SIMILES ET ADIVNGOR SI QVIS EAM TETIGIT TVNICA CREPVIT > opoudjis@optushome.com.au http:// > www.opoudjis.net > PRAVIS ARCHIPOETAE CONFESSIO EIA E CARMINIBVS BVRANIS > > > > > > > --------------------------------------------------------------------- > To unsubscribe from this mail list, you must leave the OASIS TC that > generates this mail. 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