Re: [xdi] More comments on XDI metagraph predicate examples (was: RE: [xdi] Minutes: XDI TC Telecon Thursday 1-2PM PT 2008-12-18)

[Nick Nicholas <opoudjis@optushome.com.au>]

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>

&&&
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