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Subject: Re: [xdi] Minutes: XDI TC Telecon Thursday 1-2:30PM PT 2010-10-14


as from my AP of last week, here is a message about some concerns I  
have regarding the document


Please have a focus in the main picture labelled "New View". Let's  
assume there is a node which is the "root (context)", the next node is  
a "subcontext" and the addressing mechanism suggests to use the  
statement $/=drummond/$ to address drummond's context (where =drummond  
is a label associated to the ARC connecting the root to the first  
hierarchical subcontext, i.e. =drummond)

But issues arise when we need to describe a conventional triple,  
=drummond/+friend/=markus. In this case, we have three distinct  
labels, i.e. segments =drummond, +friend, =markus. Should all these be  
associated to arcs? If this is the case, then, is it correct to say  
that all labels are "predicates"? Actually they may represent  
predicates but also subjects or objects.

So, could you please clarify precisely how subject-predicate-object of  
a classical triple are represented in this new view of the graph?

In thinking about this, I realized that you and Andy discussed many  
years ago a similar idea in the ATI model (I was not member at that  
time but I've seen some presentations on the docbox), and also that I  
was inspired by this discussion in an earlier contribution


where labels are all associated to arcs - not to nodes. Except for the  
out-of-date semantics of some operators (which refers to an older  
version of the XDI RDF model documents), maybe is it a similar view  
that you are proposing?

Kind Regards,

Def. Quota "Drummond Reed" <drummond.reed@xdi.org>:

> Following are the minutes of the unofficial telecon of the XDI TC at:
> Date:  Thursday, 14 October 2010 USA
> Time:  1:00PM - 2:30PM Pacific Time (21:00-22:30 UTC)
> Bill Barnhill
> Giovanni Bartolomeo
> Markus Sabadello
> Michael Schwartz
> Drummond Reed
> Joseph Boyle
> Joe Johnston
>      https://www2.gotomeeting.com/join/969244355
>       http://xdi.idearpad.org/10
> Please try to preface each of your comments with your name so the
> transcription into the minutes is easier.
> We went over an update to the wiki page we discussed last week (since
> renamed as follows):
>     http://wiki.oasis-open.org/xdi/MetagraphSymbols
> Bill: So what about (+x)(+y) as opposed to +x(+y)?
> Drummond: (+x)(+y) identifies the context of +y in the context of the
> context of +x while +x(+y) identifies the context of +y in the context of
> +x.
> So elsewhere in the table ((+x)) is labelled as the context of the context
> of +x. So shouldn't "the context of +y in the context of the context of +x "
> then be translated as ((+x))(+y) instead of (+x)(+y)?
> Drummond: No, because subsegment order also expresses context. For example,
> +x+y identifies +y in the context of +x.
> Bill: Ok, so I'm still unclear on the semantic difference between +x(+y) and
> (+x)(+y).  Can you describe offline if you'd like so as to not rathole..I'm
> particularly interested in how you'd differentiate these two XRIs using the
> Set membership POV.
> Drummond: I can't answer from the set membership POV yet (I need to
> understand that POV better - I'm very interested in it), but we can draw the
> graphs for each of these and that should help make it clear. What I am
> happiest about is the clear translation of XRI cross-reference syntax to
> graph notation and vice versa. It makes possible sophisticated expressions
> (such as =a/+believes/(=z/+knows/(=b/+loves/=c)) while still having
> completely unambiguous machine-understandable graphs
> See also the attached PNG file with graphics, drawn by Mike on the
> GoToMeeting screen during the call, that illustrated how cross-references
> are graphed with these semantics.
> Drummond showed an example of the simplified link contract  format that is
> possible due to the improved semantics of the metagraph  symbols. There was
> not time to go over it in depth, but we will do that next week if there is
> time. See the action item list below.
> * Giovanni will post an email about his concerns about current patterns for
> expressing subjects, predicates, objects and contexts in the XDI global
> graph
> * Giovanni will post a wiki page with his proposed set of
> constructs/operators for XDI
> * Drummond will coordinate assembly of a wiki page documenting the proposed
> link contract structure and all processing steps involved with Alice/Bob
> scenario.
> The next call is next week at the regular time. The agenda will be the
> action items listed above in the order they are listed.
> ------------
> Each of these is a candidate for the agenda for future calls.
> *  Equivalence semantics: close on whether we need an additional $ word
> that is the equivalent of Higgins Personal Data Model (PDM)  semantics  of
> h:correlation, which is not as strong as $is.
>       http://lists.oasis-open.org/archives/xdi/201006/msg00036.html
> * Cool URIs: continue previous discussion about the use of standard RDF URIs
> in XDI:
>   http://lists.oasis-open.org/archives/xdi/201006/msg00023.html

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