comments on xdi-graph-patterns

["Giovanni Bartolomeo" <giovanni.bartolomeo@uniroma2.it>]

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
>>
>>
>> PLEASE NOTE:  If the above links do not work for you, your email
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>> paste
>> the entire link address into the address field of your web browser.
>>
>> -OASIS Open Administration
>



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