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Subject: RE: [xri] Updated 2.1 ABNF and global subsegments

Hi All,
Even though Drummond and I discuss his newer proposal and explore how to make it "work", I'm not promoting it. I still favor the earlier notion of compact syntax. We never fully got compact syntax to work, but I think we were close. I think that by limiting the scope of compact syntax to a single subsegment, lots of the problems would go away. I acknowledge that the compact syntax would only work for very simple xrefs, but that was its original intent, and I kinda like that intent.
I don't like the idea of trying to get rid of parens wherever we can, because even though they make an XRI longer, for more complex XRIs they help me understand the intent of the XRI - I actually think complex XRIs that include parens are more legible than ones that don't.
Regarding the question if "=$d*2006-02-17*(=example)" and "=($d*2006-02-17)*(=example)" mean the same thing, I agree that if they normalize to the same value they MUST represent the same resource. However, these examples just illustrate that we never completed the normalization rules and syntax. If we define the scope of compact syntax to be a single subsegment, then these two XRIs are definately not equivalent (although of course they may be synonyms).
I do like the idea that bang would no longer be a GCS. As a matter of fact, I'd like for bang to continue to evolve to the point that it is just an XRI minter's claim of persistence, and have noting to do with namespace. I'd like for two XRIs that differ only in bangs to be considered equivalent for comparison and resolution. Admittedly this idea is not fully baked. 

Marty.Schleiff@boeing.com; CISSP
Associate Technical Fellow - Cyber Identity Specialist
Computing Security Infrastructure
(206) 679-5933


From: Drummond Reed [mailto:drummond.reed@cordance.net]
Sent: Wednesday, March 07, 2007 1:37 PM
To: 'Chasen, Les'; xri@lists.oasis-open.org
Subject: RE: [xri] Updated 2.1 ABNF and global subsegments

Good points/questions, Les. See [=Drummond] inline.


From: Chasen, Les [mailto:les.chasen@neustar.biz]
Sent: Wednesday, March 07, 2007 10:19 AM
To: Drummond Reed; xri@lists.oasis-open.org
Subject: RE: [xri] Updated 2.1 ABNF and global subsegments


A couple of note/comments:


* another change that this includes but does not spell out is that ! is no longer a GCS character.


[=Drummond] Good point. Standard Example #10 on http://wiki.oasis-open.org/xri/XriCd02/GlobalSubsegments shows what happens under this proposal – the former ! GCS character (which by the XRI 2.0 ABNF had to be followed by a second !, so effectively it was always !!) is now a subspace under another GCS character. For example, the XDI.org !! registry would become a subspace of the @ registry, i.e., !!1000 would become @!!1000.


* One thing that confuses me is that the second instance of a global-subseg is a xref without parenthesis but is not called a xref. 


[=Drummond] That’s a good point that was also brought up by Laurie and Marty on our XRI $ Dictionary calls. It’s purely a semantic issue, but an important one. I went back and studied the v3 proposal ABNF closely, and I came up with a solution I really like: remove the usage of “xref” altogether. See my next message to the list with a full explanation of the v4 I just posted at http://wiki.oasis-open.org/xri/XriCd02/XriAbnf2dot1.


* In this example =$d*2006-02-17=example how does that compare to =($d*2006-02-17=example) and =($d*2006-02-17)=example and =$d*2006-02-17(=example) and =($d*2006-02-17)(=example).  Do these all mean the same thing? 


[=Drummond] Marty and I went over this same question on our XRI $ Dictionary call yesterday. The first thing I need to point out is that, although we discussed not needing a delimiter before parentheses in the 2.1 ABNF, for good reasons Marty and I discovered, we do need to require one (either a GCS or LCS character). So the last two XRIs in your question should be =$d*2006-02-17*(=example) and =($d*2006-02-17)*(=example). 


[=Drummond] On the question of whether they all “mean the same thing”, there are two possible answers: a) yes, they represent the same resource because they *normalize to the same XRI*, or b) they MIGHT represent the same resource (i.e., be synonyms), but that can only be determined via resolution.


[=Drummond] For good reasons which we’ll talk about on tomorrow’s call, right now my answer would be the latter. But I plan to discuss this with Marty further before then (and if we come to solid conclusion, we’ll post it).





From: Drummond Reed [mailto:drummond.reed@cordance.net]
Sent: Tuesday, March 06, 2007 12:47 AM
To: xri@lists.oasis-open.org
Subject: [xri] Updated 2.1 ABNF and global subsegments


XRI TC Members and Observers:


An update to the proposed ABNF for XRI Syntax 2.1 has been posted to the XRI TC wiki at:




This third draft incorporates feedback and suggestions from earlier drafts. In particular it now breaks the former xri-subseg (XRI subsegment) rule into two forms: global-subseg (global subsegment) and local-subseg (local subsegment). Global subsegments replace the former compact syntax proposal. A full explanation of global subsegments and how they would be treated by XRI resolution has been posted at:




Note that the latter page still has a few TO-DOs at the end which I’ll fill in tomorrow. But I urge you to review both the proposed ABNF and the global subsegment proposal in preparation for this Thursday’s call.


Also, in a call I had with Les and Wil and Trung today, Wil took the action item to review the ABNF from the standpoint of the OpenXRI parser implementation. So he may come back with suggestions about how rule names might be refactored to best support implementation.


Please do send any feedback/comments directly to the list, as this is the last major outstanding issue for XRI Syntax 2.1, so we want to close on this and begin drafting as soon as we can to be ready for final review at the OASIS Symposium starting April 16.







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