RE: [xdi] notes from meeting in Nice, Jan 29 2009

["Drummond Reed" <drummond.reed@cordance.net>]

I'm on a plane back from my Salt Lake City trip and trying to catch up on
these recent threads. There are so many good points in Markus' original
notes, and in Nick's response, that trying to respond inline would become a
real tangle. So I'm going to pull out several individual points/open
questions and split them into separate threads.

=Drummond 

> -----Original Message-----
> From: Nick Nicholas [mailto:opoudjis@optushome.com.au]
> Sent: Monday, February 02, 2009 10:06 PM
> To: OASIS - XDI TC
> Subject: Re: [xdi] notes from meeting in Nice, Jan 29 2009
> 
> Thank you, useful to get that level of explicitness. I just discovered
> today reviewing the RDF model that = is itself an XRI for the =
> registry, so that =drummond => =/$has/drummond : your model addresses
> this nicely.
> 
> You're not making any commitment about what the relationship is
> between +x+y and +y. I had been suggesting +x+y/$is$a/+y, but after
> revisiting the RDF model (and statements such as $get$a$xsd$boolean),
> I'm not as confident about that, so you needn't change anything.
> 
> The model does not relate $has to $has$a. I think there is clearly
> such a relation --- the object of $has is the unique, possibly
> aggregate value, the object of $has$a includes those values in classes
> --- and it would be nice to have a diagram showing the relation
> between =abraham/$has$a/+son and =abraham/$has/=isaac. The
> relationship of $is and $is$a, on the other hand, was always somewhat
> murky, and it would not be useful to attempt to illustrate it.
> 
> In the new dispensation, the inverting word is $is, not $a. :-)
> 
> On 30/01/2009, at 13:15, Markus Sabadello wrote:
> 
> > Hi Giovanni (and others),
> >
> > I'm trying to summarize in a few words what we talked about. Please
> > correct me if I made a mistake or forgot anything.
> >
> > - We had a look at the xdi-rdf-global-graph-proposal-v1 which
> > Giovanni posted about a week ago:
> > http://www.oasis-open.org/committees/download.php/30802/xdi-rdf-global-
> graph-proposal-v1.pdf
> >
> > - The basic graph model described in that document is essentially
> > the same as the one we are all familiar with (i.e. subject/predicate/
> > object triples), but the document proposes a new methodology for
> > drawing the graph. The main innovation is to draw EVERYTHING that
> > has an XRI as a node (including predicates!). Arcs are drawn between
> > the nodes, but arcs themselves don't have XRIs. A typical statement
> > consisting of subject, predicate and object would be drawn as three
> > nodes and three arcs.
> >
> > - Arcs are colored to indicate which statement they belong to.
> >
> > - A node with a given XRI never appears twice in the graph, but it
> > can of course be part of more than one statement. For example if you
> > have the following two statements:
> > =markus/+email/'markus.sabadello@gmail.com'
> > +email/$is$a/+contactdata
> >
> > Then only a single node with the XRI +email would be drawn, but it
> > would be part of both statements.
> >
> > - Giovanni distinguishes between Syntactic Correctness and Semantic
> > Consistency
> >
> > - Syntactic Correctness simply means that the graph properly fits
> > into the RDF graph model (subject/predicate/object). This is a
> > similar concept to a "well-formed" XML document.
> >
> > - Semantic Consistency means that the statements in the graph are
> > consistent with accompanying dictionary statements. E.g. if you have
> > a statement =markus/+friend/=giovanni, then for the graph to be
> > "semantically consistent", there would also have to be the
> > dictionary statement =markus/$has$a/+friend. These dictionary
> > statements could be mixed into the same graph, or they could exist
> > in a separate document or XDI endpoint (such as a Community
> > Dictionary Service). This is a similar concept to a "valid" XML
> > document.
> >
> > - The XDI Validator application could be extended to support
> > validating this Semantic Consistency.
> >
> > - If you want you can work with XDI without caring about "semantic
> > consistency" / dictionary entries, just like you can work with XML
> > without caring about schemas / DTDs.
> >
> > - Giovanni's document also introduces the concept of "roots", which
> > are drawn as a slash in a box. Those roots and the arcs originating
> > from them do not actually appear as statements in the graph, but
> > they indicate who is authoritative for an XRI. For example, all +
> > XRIs (+friend, +email, etc) come from the same "root" (the Community
> > Dictionary Service). Similarly, all $ XRIs ($is, $has, etc) come
> > from the same "root" (the XDI specfications). =markus and =drummond
> > would come from different "roots", since different XDI endpoints are
> > authoritative for them.
> >
> > - We talked a bit about equivalence. Giovanni thinks that if there
> > is a $is statement between two XRIs, then those two XRIs are drawn
> > as only a single node in the graph. So the node would have two XRIs
> > that identify it. Markus mentioned that is not how his
> > implementation currently works.
> >
> > - A question that follows is how would XDI messaging be affected by
> > the above. For example, if you have the following XDI graph:
> >
> > =markus
> >     $is
> >         =markus.sabadello
> >     +name
> >         "Markus Sabadello
> > =markus.sabadello
> >     +nationality
> >         "AT"
> >
> > And if you then send this XDI message:
> >
> > =giovanni
> >     $get
> >         /
> >             =markus
> >                 +nationality
> >
> > Would there be a reply ("AT"), or would there be no reply?
> >
> > - A similar example would be the effect of a $del message. If
> > equivalent XRIs are drawn as only a single node in the graph, and
> > you remove the $is statement via a $del message, would the node then
> > "split up" into two nodes?
> >
> > - Giovanni gave a demo of a project his team has been working on
> > ("SMS" - "Simple Mobile Services" - www.ist-sms.org). It allows
> > users to send small notes about people, locations, services, web
> > sites, etc from their mobile phone to a server. These notes (so-
> > called MEMs) are then shared with an online community. It's possible
> > to advertise and discover new services. Phone security features such
> > as encryption via the SIM card are used. Various authoring tools are
> > available for creating new Simple Mobile Services that communicate
> > via MEMs. A web portal makes it possible to collect and analyze the
> > data that was collected by the system.
> >
> > - Giovanni explained that many of his XDI inputs were motivated by
> > use cases in the SMS system, e.g. XDI Queries.
> >
> > - We both think it was a good idea to have a chatroom during the
> > last TC call. We should always use that from now on.
> >
> > Markus
> >
> 
> (*)(*)(*)
> http://www.opoudjis.net      DR NICK NICHOLAS; LINK AFFILIATES,
> MELBOURNE
> skype:opoudjis              opoudjis@optushome.com.au
>   "Some of the English might say that the Irish orthography is very
> Irish.
>   Personally, I have a lot of respect for a people who can create
> something
>   so grotesque." -- Andrew Rosta
> 
> 
> 
> 
> 
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