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Subject: RE: [xri] GCS Characters

The GCS Delimiter proposal (http://wiki.oasis-open.org/xri/XriThree/GcsDelimiter) goes into great depth about why XDI needs the level of precision provided by both GCS delimiters and cross-references. Cross-reference syntax (syntactically encapsulating identifiers by enclosing them in parentheses) is essential for being able to put any identifier (a URI or an XRI) in another context. For example, in my last message I showed how it could be used to indicate – anywhere within an XRI – that a URI represented a resource in either a personal or an organizational context:





This isn’t something we want to give up.


At the same time, the extreme semantic precision of XDI RDF (which is really to say the extreme semantic precision of any RDF vocabulary compared to natural language vocabularies like English) also needs to be able to express that a resource in one XDI global context can be referred to directly within another XDI global context. That means the ability to express any combination of the following XRIs:














In XDI RDF, all of these represent very precise RDF statements about the relationship between two resources that can be independently identified in a global context. Adding parens, stars, or bangs would change those XDI RDF statements as explained at http://wiki.oasis-open.org/xri/XriThree/GcsDelimiter.


In conclusion, Les, I don’t think there is any satisfactory answer to your question when you are looking at XRI syntax from a natural language standpoint. To a human being, =drummond@microsoft.com and =drummond*(@microsoft.com) don’t look that different. However to a machine, they are different identifiers, and when you need the precision of a semantic language like XDI RDF, this difference becomes critically important.


On that score, for TC members who are not intimately familiar with RDF, I did a blog post about a new book called Semantic Web for the Working Ontologist:




I recommend it very highly because it does such a good job at explaining to reasonably web-savvy technologists how RDF really works and what kinds of problems in machine-understandable semantics it can solve.




From: Chasen, Les [mailto:les.chasen@neustar.biz]
Sent: Monday, November 24, 2008 11:36 AM
To: drummond.reed@cordance.net; xri@lists.oasis-open.org
Cc: jbradley@mac.com; victor@idcommons.org; orchard@pacificspirit.com
Subject: Re: [xri] GCS Characters


I continue to struggle with why we need two ways to put a global xri in the context of another xri. =drummond@microsoft.com and =drummond*(@microsoft.com) seem to do the same thing. If the later is less than desirable let's drop ()'s in xri.

Besides that confusion there is the issue steve raises.

From: Drummond Reed
Cc: 'John Bradley' <jbradley@mac.com>; 'Victor Grey' ; Chasen, Les; 'David Orchard'
<orchard@pacificspirit.com>Sent: Mon Nov 24 14:07:53 2008
Subject: RE: [xri] GCS Characters

First, just to address some clarification questions in this thread, the proposal under discussion, called GCS Delimiter, is posted at:




The accompanying ABNF that implements this proposal is at:




As described there in more detail, the proposal is that in XRI 3.0, all GCS characters (=, @, +, $) are treated in XRI syntax as delimiters just like * and ! are in XRI 2.0.


Per the ABNF, both =drummond@microsoft.com and @microsoft.com=drummond would parse into two subsegments. =drummond@microsoft.com would parse into:


1) =drummond

2) @microsoft.com


@microsoft.com=drummond would parse into:


1) @microsoft.com

2) =drummond


=drummond+phone+home would parse into:


1) =drummond

2) +phone

3) +home


In XRI resolution, each of these would produce its own XRD. I don’t know why John thinks this is strange – an XRD can describe any resource, and certainly my phone collection is a resource, and my home phone is a resource.





From: John Bradley [mailto:jbradley@mac.com]
Sent: Monday, November 24, 2008 10:47 AM
To: Victor Grey
Cc: Chasen, Les; Drummond Reed; OASIS XRI TC; David Orchard
Subject: Re: [xri] GCS Characters


Well thats a can of worms:)


I think in Drummonds proposal + and $ also get to have XRD.  


In the first segment the only place those symbols formerly known as GCS would have there conventional meaning is if they are attached to the first sub segment.


If they are the leading character of any other subsegment they would be treated as * and the =, +, $ are only inferences to the global concept.


Remember I am the one opposed to the change unless there is a good reason.   So take any pro things I say with a grain of salt.


The thing is that under that they will be treated as sub segments by the authority server,  so what gets passed?


For =drummond@microsoft.com  the first subsegment is =drummond what is the second that get passed to =drummonds's authority service?






So would =drummond*microsoft.com produce the same XRD as =drummond@microsoft.com?


Could go ether way depending on how we define resolution.


Yes having =drummond+phone have its own XRD seems sort of funky to me as well.


John B.


On 24-Nov-08, at 10:23 AM, Victor Grey wrote:


The confusion with email addresses, social, technical or otherwise, is not the only problematic aspect of the @ GCS character.
XMPP addresses take the form of username@host/optional/path. The username part (known as a JID or Jabber Identifier) has only a very few disallowed characters, including whitespace and control chars and : / " ' and of course @.

The = and @ GCS characters both denote a reassignable identifier for an entity, as opposed to + and $ which identify terms.
@ and = also serve as configurable aliases for an XRD discovery function $f(x), for example $dns(xri.net).

If we didn't have to deal with @, we could define a very simple and expandable set of transformations for XRD discovery:
Given an abstract ID =drummond with $f(x) configured as $dns(xri.net), here are some possible discovery transformations:
https               https://xri.net/=drummond
http                 http://xri.net/=drummond
xmpp              =drummond@xri.net
mailto =drummond@xri.net (I think there is an attractive case for an XRI aware mailserver that can resolve the XRI and make service selections based on the XRD and x-headers.)

Other as yet to be invented communication protocols could all be accommodated with this simple and very abstract spec. We shouldn't let the current kerfluffle with the W3C derail us into thinking that http is the whole universe of possibility.

Since @ and = behave exactly the same way, and =ids --can-- be used as community roots already, I've never really understood any strong necessity for the overloading of the entity identifier to distinguish individuals from collections of individuals, and the disregard of the fact that there could be other kinds of entities besides those two.

So at the risk of making everyone's head explode, I'm proposing that we deprecate the @ GCS character in XRI 3, and make = the single GCS character that denotes a reassignable identifier for any kind of entity. An entity would be defined as anything that can have an XRD.



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