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Subject: RE: [xdi] on global cross references and the link contract use case

Les, I strongly disagree that GCS delimiters is “a solution looking for a requirement”. Not even in the early days of “concatenated syntax” was that true. However it is true that it wasn’t until the work of the XDI TC on the XDI RDF model that we were able to articulate the requirement for ordered sets of XRIs in detail.


The XDI TC contributed the http://wiki.oasis-open.org/xri/XriThree/GcsDelimiter page to the XRI TC to document this requirement so it would be clear. I understand you are telling us it doesn’t explain it clearly enough to you.


Let’s move to voice. I’ll try to call you now. It may be too late today to reach you given that tomorrow is Thanksgiving, but if we don’t talk today, let’s try to hook up Friday or Monday.






From: Chasen, Les [mailto:les.chasen@neustar.biz]
Sent: Wednesday, November 26, 2008 1:56 PM
To: John Bradley
Cc: giovanni.bartolomeo@uniroma2.it; xdi@lists.oasis-open.org
Subject: RE: [xdi] on global cross references and the link contract use case


See below for some specific responses.  Overall I am still just not getting the need for this capability.  This proposal has been out there, under various names, for years.  OMG, I cannot believe it has been years L


The problem, IMHO, is that a solution was discovered before a requirement or need came to light.  Almost by mistake this solution, originally called concatenated syntax, was discovered while explaining XRIs to others.   This syntax seemed easier to convey the message.  Once we had this solution a requirement was sought out.  That is a bit backwards.  Usually one comes up with a requirement before figuring out a solution.  As a result we have been trying to fit a requirement into the solution and none of them seem to have been articulated very well.    I just do not understand why we need to introduce global subsegements.


From: John Bradley [mailto:jbradley@mac.com]
Sent: Wednesday, November 26, 2008 1:30 PM
To: Chasen, Les
Cc: giovanni.bartolomeo@uniroma2.it; xdi@lists.oasis-open.org
Subject: Re: [xdi] on global cross references and the link contract use case


We need to remember that @cordance is not asked.


If @cordance has an authority service that service is asked for a XRD.  

[Chasen, Les] Right, the authority resolution service for @cordance is providing the responses.


The Authority service for @cordance can produce a XRD in any way it sees fit.  It may take it from a file or look it up in XDI or some other database.

[Chasen, Les] Correct


I think the Parenthesis indicate that the thing it is being handed to resolve is not a normal subsegment it must use some special processing to produce a XRD for the identifier contained in the cross reference.

[Chasen, Les] Interesting … Now the parenthetical cross reference is being referred to as not normal.  I am not sure I agree but if it is special processing seems to make sense.  However, special processing has not been proposed.


Passing *(=Drummond) to a authority server is telling the authority server to produce a XRD based on the input value of the global =drummond.   It could just go get =Drummond's XRD and return that though that would brake CID verification.  

[Chasen, Les] it could but again special processing has not been proposed.  It would seem that if there really is a significant difference between GCS subsegments and cross references that there should be.  I am trying to understand this.



I see the (=drummond ) , (+14165551212) or (http://yahoo.com) etc as inputs to some lookup extension process on the authority server,

and =drummond as a subsegment a request to retrieve that subsegment from @cordance's authority server.

[Chasen, Les] At this point I just do not see the justification for this. 


Cross references have always been about sending an opaque string to a authority server to get back a XRD.

[Chasen, Les] an opaque string that represents another authority.


I don't thingk @cordance+drummond is a cross reference it is a two subsegment XRI

[Chasen, Les] I do not agree.  




On 26-Nov-08, at 10:02 AM, Chasen, Les wrote:


I need to stick with simple examples and in this case there is only one authority, @cordance, in question. under the current proposal @cordance is asked for both =drummond and *(=drummond) and it returns its own xrd if one exists within @cordance. We have never discussed whether @cordance may go to the = authorty server for drummond when it is contained within *(=drummond). I think that maybe interesting behavior.



From: John Bradley
To: Chasen, Les
Cc: giovanni.bartolomeo@uniroma2.it ; xdi@lists.oasis-open.org
Sent: Wed Nov 26 12:44:00 2008
Subject: Re: [xdi] on global cross references and the link contract use case




I started off with that position.   I now think they are separate queries to the next authority server.


I think that the parenthesized statement may contain multiple subsegments is the important thing.  

Once we have a way to encapsulate multiple subsegments to be handed to an authority server it is hard to stop someone from only putting in a single subsegment. in the cross ref.


I think the simple principle is that things in parenthesis are opaque to the resolver and handed to the next authority server and things not in parenthesis are resolved left to right one subsegment at a time.


I also don't think that in ether case @cordance is being asked anything about the global =drummond if one exists.


In the first case the authority server for @cordance is being asked for a XRD for the subsegment =drummond the = is treated as part of the subsegment itself

In the second  case the authority server for @cordance is being asked for a XRD for the subsegment  *(=drummond) 


I think the latter could be taken that the authority server may look someplace else to get the XRD for the cross reference.

I think in the former case =drummond is a subsegment in its authority server.


The question is if it is just a regular subsegment is using = as a separator going to confuse people.


=drummond is just a regular subsegment with some inference by Cordance that its =drummond has something to do with the global =drummond though XRI makes no such claim other things using XRI like XDI may.



John B.



On 26-Nov-08, at 9:23 AM, Chasen, Les wrote:


Let's not complicate this with +phone. My question is does @cordance return a different xrd for =drummond and *(=drummond)? This proposal says yes. I disagree with this behavior. I think @cordance is being asked for its representation of =drummond in both cases.



From: John Bradley
To: Chasen, Les
Cc: giovanni.bartolomeo@uniroma2.it ; xdi@lists.oasis-open.org
Sent: Wed Nov 26 12:11:59 2008
Subject: Re: [xdi] on global cross references and the link contract use case


From a XRI resolution perspective I see a difference in what @cordance's authority server is asked for.


@cordance=drummond                                , @cordance is asked for the XRD for =drummond

@cordance=drummond+phone        , @cordance is asked for the XRD for =drummond , @cordance=drummond is asked for the XRD for +phone

@cordance*(=drummond)                , @cordance is asked for the XRD for *(=drummond)

@cordance*(=drummond+phone)    , @cordance is asked for the XRD for *(=drummond+phone)


Parenthesis in the first segment tell the resolver to treat the contents as an opaque string and pass it to the next authority server.


The resolver Parenthesis in the path are not significant to the resolver they would be matched during service selection as they are now.


One thing we did start talking about at the F2F is what the syntax to indicate special processing on a cross reference.


An example:


Is $XRD a node that has as its authority service one that performs XRD resolution on the next subsegment.


So is a $ word in XRI resolution a node that points to a specialized authority service?


Certainly a resolver has the option of shortcutting resolution through querying the $XRD authority server if it understands the $XRD word.


Under Drummond's proposal we do have to have a theory about what + and $ in the first subsegment resolve to.


John B.



On 26-Nov-08, at 6:51 AM, Chasen, Les wrote:


Hi Giovanni -

A cross reference is putting the thing cross referenced inside the context of the xri that contained the cross reference. Terminology in this proposal has been changing but the thing that hasn't is that in both cases the outer authority is returning its xrd for the reference. That is, in the example below, cordance is returning its xrd for =drummond.


So we only support the 'inside' (or better stated container) concept. Now it may be interesting to consider a resolution process which rather than asking @cordance for =drummond we ask = for drummond. Today that does not exist.

Have a happy thanksgiving.





From: Giovanni Bartolomeo
To: Chasen, Les
Sent: Wed Nov 26 09:35:43 2008
Subject: RE: [xdi] on global cross references and the link contract use case


Hello Les,

First, thank you for having read the contribution! Unfortunately I'm probably not the best person which can answer your question, as I'm not an expert of XRI2.0. I limited to develop my contribution in the scope of the current proposal ( http://wiki.oasis-open.org/xri/XriThree/GcsDelimiter), which, I personally support for one specific reason: http://lists.oasis-open.org/archives/xri/200811/msg00043.html.

I think Drummond's reply http://lists.oasis-open.org/archives/xdi/200811/msg00031.html is a good technical explanation of this, expecially the last statement: in an ordered set, you are not referencing across contexts. The context is the ordered set itself. For example, in $sig$d, the context for $d is $sig. Which I understand as follow: put an object inside a context is not exactly the same as referencing it from that context).

The core of this issue - that's my guess and not a technical explanation -  is probably that XRI2.0 did not consider the need to "put an instance of an object inside a context", but just to "cross reference" it. That is instead a fundamental capability for XDI (and for any human or machine understandable language).

I'll be happy to answer any further questions you might have on the contents of the contribution itself.

Kind Regards,

At 13.36 25/11/2008, Chasen, Les wrote:

Hi Giovanni.  I had a chance to read this.  While I like what you guys
are doing with link contracts I fail to understand why all of these
examples do not work with XRI 2.0 style cross references. 

> -----Original Message-----
> From: Giovanni Bartolomeo [ mailto:giovanni.bartolomeo@uniroma2.it]
> Sent: Wednesday, November 19, 2008 12:02 PM
> To: XDI
> Subject: [xdi] on global cross references and the link contract use
> case
> Hello,
> some weeks ago I mentioned that I was playing a bit with the
> semantics of link contracts. Better to say, with the global cross
> references applied to the link contract use case. After the issue of
> XDI RDF model v.11, I put my thoughts in a document which you can find
> below.
> Maybe just semantic nuances, but your comments will be welcome.
> Thanks,
> Giovanni

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