Re: comments on xdi-graph-patterns

[Drummond Reed <drummond.reed@xdi.org>]

Giovanni et al,

RE the self-referential arc notation, I had a key realizatiion after reading your message, which is that using the new graph notation, synonyms can all be expressing using relational arcs with the $ metagraph symbol. I had simply never realized that option, and it works wonderfully, eliminating the need for there to be any special exceptions to the graph notation. All synonyms are expressed cleanly as relational arcs either between two context nodes, or between a root context node and a context node.

I was so happy about this I have already updated the XDI Graph Patterns PPT and PDF to show this new synonym pattern in all the diagrams.

RE the versioning pattern, you bring up some very good points about data duplication. I will add this to the agenda for tomorrow's call because it is a fascinating discussion about how to solve that efficiently.

I'll send the agenda next.

Talk to you tomorrow,

=Drummond

On Wed, Mar 2, 2011 at 6:00 AM, Giovanni Bartolomeo <giovanni.bartolomeo@uniroma2.it> wrote:

Dear Drummond and all,

in preparation for next tc call, here is a couple of comments on this document xdi-graph-patterns-2011-02-18.pptx

These comments are about the diagram at page 3 so that once solved we hopefully will be able to quickly proceed with the rest of the document.

- about versioning. Perhaps, the two arcs !1, !2 under the context =abc+age$v,  should point to another node (instead of providing directly a value) represeting a version of the original node  +abc+age at that time.

Note that this may include e.g., all attributes which that node had at that time, including the versioning attribute. I.e. +abc+age at version $v!3 should have versioning attributes $v!2 and $v!1, whereas +abc+age at version $v!2 should have only one versioning attribute, $v!1.

Going deeper into this is made more complex as we are dealing with a literal, but I think there is a solution for this. More in next phc...

- about the self referencial arc. Hereafter some comments about, taken from the wikipage

http://wiki.oasis-open.org/xdi/XdiGraphPatterns

GB: I don't think that a self referential arc is the best way to visually depict XDI synonyms in a graph. I propose a different representation: a XDI synonym is a contextual arc (or a path made of contextual arcs and contextual nodes) that ends exactly at the same contextual node. This has been illustrated in the graph above with a blue arc - please note that the usage of a different color is only for illustration purposes and is not part of the proposal

DR 2010-12-23: I have reviewed the options and arrived at the conclusion that the self-referential arc is still the only logically consistent way for any XDI context node to be able to assert the *set of synonyms of which that node itself has knowledge*. Such synonyms are expressed as XDI statements in the form xdi-address/$/synonymous-xdi-address. Following the rules of the graph notation, where every first-segment subsegment represents a contextual arc, the only way to graph such a statement is to show a self-referential contextual arc at a context node that shows the name of the synonym (which may be multiple subsegments) as the name of the arc [...]

These comments were written before we agreed on the way to represent synonyms: contextual arcs poiting to the same node in the global graph.

If the matter is to express the *set of those synonyms*, we should just use <xdi-address>$, which derives from <xdi-address>/$/<synonymous-xdi-address> and is as usual a concatenation of subject <xdi-address> with predicate $ (consistently with the usual notation =drummond+friend which represents the set of drummond's friends given the statements =drummond/+friend/=markus, =drummond/+friend/=giovanni, etc. ...)

More in next phc... hopefully.

Best Regards,
Giovanni

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

I too will be tied up in meetings in San Francisco on Thursday, so with Bill
also gone, I suggest we cancel that call this week. I am still tentative for
Friday's OpenXDI Project call -- I'll do my best to make that one (I should
know by Thursday if I have a conflict).

=Drummond

On Tue, Feb 22, 2011 at 11:51 AM, Barnhill, William [USA] <
barnhill_william@bah.com> wrote:

I will be at a client conference for the rest of the week so will be unable
to attend either call.
I plan on attending regularly again as of next week.

-Bill
________________________________________
From: drummond.reed@xdi.org [drummond.reed@xdi.org]
Sent: Friday, February 18, 2011 2:01 PM
To: xdi@lists.oasis-open.org
Subject: [xdi] Groups - XDI Graph Patterns 2011-02-18 - PDF
(xdi-graph-patterns-2011-02-18.pdf) uploaded

PDF of previous doc

 -- Drummond Reed

The document named XDI Graph Patterns 2011-02-18 - PDF
(xdi-graph-patterns-2011-02-18.pdf) has been submitted by Drummond Reed to
the OASIS XRI Data Interchange (XDI) TC document repository.

Document Description:
PDF version of XDI Graph Patterns - fixed two errors in last version

View Document Details:
http://www.oasis-open.org/committees/document.php?document_id=41204

Download Document:

http://www.oasis-open.org/committees/download.php/41204/xdi-graph-patterns-2011-02-18.pdf


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