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Subject: RE: [xri] Proposal for XRI Syntax 2.1 to treat all delimiters as signficant

Title: Re: [xri] Proposal for XRI Syntax 2.1 to treat all delimiters as signficant

Marty, I’m tied up until 11AM PT tomorrow, but if we could talk sometime between 11AM and 1PM PT tomorrow, that would be great. I’ve no idea if Les or Wil or anyone else is available at that time, but I’ll check with Les in the morning, and whatever time we choose we’ll publish a telecon number to the TC list so anyone else who is available can join us.


Also, you mention being available for 90 minutes following the TC call on Thursday – do you mean from 10AM to 11:30AM PT? If so, the TC call begins at 10AM PT, so we could spend the first hour on XRI resolution issues and then switch to ABNF discussion at 10AM when you are able to join us.


I suspect that in two sessions, one tomorrow and a second on Thursday, we could make substantial progress.




From: Schleiff, Marty [mailto:marty.schleiff@boeing.com]
Sent: Tuesday, March 13, 2007 5:56 PM
To: Drummond Reed; Chasen, Les; xri@lists.oasis-open.org
Subject: RE: [xri] Proposal for XRI Syntax 2.1 to treat all delimiters as signficant


On Wednesday I'm can be available between 7:30 and 9:00, and then again from 9:30 tyo 1:00 (Pacific).

On Thursday we could use the 8:00-9:00 Metadata call for this discussion. I'm also available for 90 minutes following the XRI TC call.

On Friday I have only one obligation, between 9:00 and 9:30.

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: Tuesday, March 13, 2007 4:51 PM
To: Schleiff, Marty; 'Chasen, Les'; xri@lists.oasis-open.org
Subject: RE: [xri] Proposal for XRI Syntax 2.1 to treat all delimiters as signficant

Thanks, Marty and Les, this is a healthy discussion. I suspect it will be hard to advance it much more via these email messages; the thread is already quite long. I expect we need some one-on-one discussions and/or several TC calls devoted to this subject to arrive at a consensus.


Marty, your voice is critical but right now I know you have a conflict with our new Thursday 10AM PT telecon time. Is there a time either tomorrow or at a different time on Thursday or Friday when you would be able to telecon with Les and I and any other TC members that are able to join?




From: Schleiff, Marty [mailto:marty.schleiff@boeing.com]
Sent: Tuesday, March 13, 2007 3:46 PM
To: Chasen, Les; Drummond Reed; xri@lists.oasis-open.org
Subject: RE: [xri] Proposal for XRI Syntax 2.1 to treat all delimiters as signficant


<marty>Well, my kids tell me I'm not cool, and in this case they're correct. I may eventually get cool, but I'm not there yet. I've made my responses in fuscia below. Please don't take my silence on other messages to imply consent. I'm slow, and my response to this message took me over an hour, so I can't possibly respond to everything. However, even if my consent is not obtained, in the interest of making progress I will bend to the will of the TC.</marty>


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



From: Chasen, Les [mailto:les.chasen@neustar.biz]
Sent: Tuesday, March 13, 2007 2:21 PM
To: Drummond Reed; Schleiff, Marty; xri@lists.oasis-open.org
Subject: RE: [xri] Proposal for XRI Syntax 2.1 to treat all delimiters as signficant

IMO, that introduces confusion and therefore complexity but that is just my opinion.  I have said it before and I’ll say it again, there is nothing more important, IMHO, than getting to the standards track.  If Wil, Marty, Steve, Gabe and the other members of the team are cool then I will be.


contact: =les

sip: =les/(+phone)

chat: =les/skype/chat



From: Drummond Reed [mailto:drummond.reed@cordance.net]
Sent: Tuesday, March 13, 2007 4:59 PM
To: Chasen, Les; marty.schleiff@boeing.com; xri@lists.oasis-open.org
Subject: RE: [xri] Proposal for XRI Syntax 2.1 to treat all delimiters as signficant


Les, I should point out that =drummond+phone and =drummond*(+phone) differ not just in parentheses, but also in the use of a local context symbol. 


<marty>Drummond, when you're answering questions now, you're answering as if the new proposal is the gospel. For myself (and possibly others) "=drummond+phone" and "=drummond*(+phone)" are still equivalent, so there's no difference. They both use a local context symbol, implied in one, and explicit in the other. </marty>


If we look for a direct analogy in the English language (and I want to be careful to point out that: a) this is just an analogy to a human langauge, and b) this particular analogy is to English; the comparison may be different in other languages), we could ask if the following two phrases are different?


            Drummond’s phone

            Drummond’s “phone”


At least to me, as a writer, the second sentence has a subtle but distinctly different meaning than the first. The first one corresponds to the globally-understood (by English-speaking readers) meaning of the word “phone”. The second one, by using quotes, suggests that there is a special *locally-understood meaning* of the word “phone”.


While that latter meaning MIGHT be the same as the former meaning, it also clearly MIGHT be different. Therefore the two sentences cannot and should not be assumed to be equivalent.


I believe the same should apply to =drummond+phone and =drummond*(+phone).




From: Chasen, Les [mailto:les.chasen@neustar.biz]
Sent: Tuesday, March 13, 2007 1:40 PM
To: Drummond Reed; marty.schleiff@boeing.com; xri@lists.oasis-open.org
Subject: RE: [xri] Proposal for XRI Syntax 2.1 to treat all delimiters as signficant


I personally don’t see it as *significantly* easier.  However, if the rest of the TC does that is fine.  I do feel that saying two XRIs, that are different only in the parens, are not the same is confusing.

Why should =drummond+phone be different than =Drummond*(+phone)? 



contact: =les

sip: =les/(+phone)

chat: =les/skype/chat



From: Drummond Reed [mailto:drummond.reed@cordance.net]
Sent: Tuesday, March 13, 2007 4:20 PM
To: Chasen, Les; marty.schleiff@boeing.com; xri@lists.oasis-open.org
Subject: RE: [xri] Proposal for XRI Syntax 2.1 to treat all delimiters as signficant


Les, Marty, see [=Drummond] inline in both your messages below.


From: Chasen, Les [mailto:les.chasen@neustar.biz]
Sent: Tuesday, March 13, 2007 5:57 AM
To: marty.schleiff@boeing.com; drummond.reed@cordance.net; xri@lists.oasis-open.org
Subject: Re: [xri] Proposal for XRI Syntax 2.1 to treat all delimiters as signficant


I think you and I are mostly in agreement on the use of parens.  The thing I don't understand is how removing the parens in a cross reference makes it significantly easier for humans to read and write XRIs. 

[=Drummond] I believe the motivations for the global ref proposal is very simple and clear: it allows you to concatenate two or more single-segment absolute XRIs directly, with no special rules about the use of delimiters or parentheses.

For example, take the following XRIs, all of which are independently syntactically valid absolute XRIs:





Under the global refs proposal, you can compose composite XRIs out of these component XRIs via direct contatenation without any special rules. Examples:







I suspect that XRI TC members have been working with parenthetical encapsulation of cross-references for so long that the notion of direct concatenation of global references seems foreign. However my experience with individuals outside of the TC is exactly the opposite. Since they’ve never seen parenthetically-encapsulated identifiers, direct concatenation is completely intuitive to them, whereas the concept of parenthetially-encapsulated identifiers is foreign and must be learned. 

<marty>I suspect that Drummond been working with Global-Refs for so long that the notion of parentheses to indicate a reference almost seems foreign. When I showed the v2.0 schema to a colleague at another company, he read an accompanying paragraph and immediately recognized what was meant by the parentheses (obviously he's lots smarter than me). So, my experience has been that the use of parentheses is understandable (which is a good thing because the Global-Refs proposal still needs parentheses for the cases Drummond described below). As I read Drummond's experiences about other people's intuitive reaction, I also thought it would be nice to conduct some sort of survey, because I agree that by now we're probably all too close to this to recognize what is intuitive to a new-comer.</marty>

I would go so far as to say that direct concatenation of identifiers is so simple, intuitive, and useful that as a TC we should be taking the opposite stance and asking how can we ELIMINATE the need for parenthetical encapsulation wherever possible. When you take this perspective, the places where we have found parenthetical encapsulation is unavoidable is:

* Using URIs as cross-references (because URIs have a different syntax)

* Using multi-segment XRIs as cross-references (because you need to know where the cross-reference ends)

* Using multiple cross-references as a single cross-reference (because you need to know where the cross-reference ends)

Direct concatenation works in all other cases, so I submit that these should be the only three cases where parenthetical encapsulation is necessary.

See more [=Drummond] inline in Marty’s message below.

----- Original Message -----
From: Schleiff, Marty <marty.schleiff@boeing.com>
To: Chasen, Les; Drummond Reed <drummond.reed@cordance.net>; xri@lists.oasis-open.org <xri@lists.oasis-open.org>
Sent: Tue Mar 13 03:21:42 2007
Subject: RE: [xri] Proposal for XRI Syntax 2.1 to treat all delimiters as signficant

Hi All,

Les, as I understand it Drummond's proposal is NOT to make the parens
optional. If there are parens present, then they were explicitly put
there for a reason (although I can't understand what such a reason would
be), and the XRI is NOT equivalent to a similar XRI without parens. So,
normalization would NOT remove any parens.


[=Drummond] Correct. By the logic above, if an XRI author has a reason to not use direct concatenation where it would be syntactically valid, that reason is known to the author and should not be overrided by XRI normalization rules.

I don't favor the proposal. I want the use of parens to be more
intuitive, and the notion of parens being used to add clarity even if
they are not required is pretty intuitive to me.


[=Drummond] While I understand this sentiment, I believe it needs to be weighed against the simplicity and intuitiveness of direct concatenation. I doubt anyone on the TC would argue that direct concatenation is the simplest and most intuitive method of identifier construction there is. After all, every single sentence I’m writing here is composed of directly concatenated words (where spaces are the delimiter). 

<marty>The concatenated words in this sentence have no hierarchical relation to the others. "Every single sentence I'm writing here after all, is composed of words directly concatenated (where spaces are the delimiter)". My sentence means the same thing as your sentence in the prior paragraph, even though the words are in a different order. You can't do that with XRI. If we want to use natural language as identifiers, then mine would be "the overweight guy from Boeing that likes XRI, but doesn't like the Global-Refs proposal", whereas Greg would be either "Greg" or "the physically fit guy from Boeing that likes XRI, but doesn't have a clue about Global-refs, but is getting a little tired of waiting for the spec to mature". Oops! someone might think those aren't good identifiers because they're not opaque!

[=Drummond] I’ll go on record as saying that I believe the TC would be making a tremendous mistake if, simply because of our evolutionary path in figuring this all out, we ignore the power of direct concatenation in the construction of XRIs. I can’t count the number of times that developers, when first exposed to XRI syntax, have asked me, “Can’t you get rid of those complicated parentheses?” 

<marty>Although I'm not a hard core developer, I am one of the people who repeatedly whine about what I consider "over-support" of xrefs. But Drummond, please recognize that I'm not complaining about parentheses; instead I'm complaining about supporting the notion of xref in so many of our ABNF rules. For example, if "$l" really refers to RFC3066, why do we need to support "$l*(xref)"? An answer I keep hearing is "for extensibility". Let the people responsible for RFC3066 extend it. If we want some namespace for languages not covered in RFC3066, we could just set up another namespace (or anybody else could)to name other languages -- maybe intergalactic languages aren't covered in RFC3066, so someone might establish "$igl" to hold inter-galactic languages, or some other namespace not even under "$". Anyway, enuf ranting about that.</marty> 

[=Drummond] But you don’t need to take my word for it. If it would be more scientifically objective for us to get the opinions of developers, Internet architects, and others outside the TC about the relative value of direct concatenation vs. parenthetical encapsulation, I’d be happy to help organize a feedback session.

I still suggest that
several of the issues with the earlier "compact syntax" proposal would
not be issues at all if we limited the scope of compact syntax to a
single subsegment. Then "$(http://example.com)=gmb*sub1" would clearly
be equivalent to "$(http://example.com)*(=gmb)*sub1" and clearly NOT
equivalent to "$(http://example.com)*(=gmb*sub1)".


[=Drummond] Ironically, the proposed normalization rule – that all delimiters be considered significant – already tells you that these three XRIs are not equivalent.  

<marty>The "proposed normalization rule" only tells us that these three XRIs are not equivalent IF the proposal gets accepted.</marty> 

 This seems intuitive
to me, because it's more like the mathmatical concise interpretation of
parens (as opposed to the grammatical willy-nilly use of parens -- where
it's up to the author to determine if parens have the same meaning as
commas or hyphens -- or if some other punctuation should be used).


[=Drummond] Although I too have been tempted by a mathematical interpretation of parentheses in the past, I now believe its a red herring. Identifiers are not operators. They are identifiers. They identify resources using a sequence of characters. Therefore the fewer normalization rules that are necessary to change this sequence of characters, the better.

<marty>I don't mean that parens should be treated exactly like they are in math; instead, I mean the definition of how to treat parens should be concise (like the math usage is concise vs. the english usage is pretty free-form).</marty>

Identifiers are used to look up things, and looking things up requires
matching rules, and matching rules are frustrated by syntax that's not


[=Drummond] Agreed. I believe that the syntax in http://wiki.oasis-open.org/xri/XriCd02/XriAbnf2dot1 is the most precise we’ve ever had, and the corresponding normalization rules are the simplest we’ve ever had.

I also don't like the new proposal's notion of an empty ref-value
because I can't comprehend what it means. It is certainly not intuitive
to me. I think the notion seems contrived and that it just exists to
make the syntax proposal work - not a very noble reason.


[=Drummond] All the proposed 2.1 ABNF states is that a ref-value to be optional, which is no different that the 2.0 ABNF. An empty ref-value is no different than an empty subsegment or an empty segment. We didn’t invent the concept of an empty segment -- URI and IRI have long explicitly supported that concept. In URI and IRI syntax, every segment contains a ref-value (they don’t call it that, but it’s the same thing), and it’s not required, so it can be empty.

[=Drummond] There are many uses for an empty segment, although I would say that few if any of them are “intuitive”. Like the number zero, its inherently a complex concept. 

<marty>So far I have heard zero uses for an empty segment, and I don't understand a single one of them. Does anyone have an example?</marty>  

Sadly, I don't know how the older compact syntax proposal can do for the
XDI use case of double parens (which BTW is yet another use case I don't


[=Drummond] I strongly believe that at this point we need to generalize from specific use cases to general principles. We have spent several years developing XRI syntax to meet an overall set of design principles. The proposal at http://wiki.oasis-open.org/xri/XriCd02/XriAbnf2dot1 is the simplest and most general ABNF we’ve ever had. To Steve’s point, it is now as close to a completely abstract syntax as we have been able to get.

[=Drummond] The key point I’m trying to make it that designing the syntax to the Einsteinein dictate of “as simple as possible but no simpler” means that we will have done our best to design a syntax that can be adapted to hundreds of future use cases for identifiers that we have never anticipated, just as we have use cases today that we never anticipated three years ago. To use parenthetical encapsulation as an example: who are we to say to say to the XDI TC – or any any future producer of XRIs and XRI-based identifier construction algorithms – that double or triple or quadruple parentheses should not be significant? The fact that the XDI TC was the first to come up with that usage reinforces for me the importance of keeping the rules as simple as possible: if all delimiters are significant, then its very clear what XRIs can be evaluated as equivalent directly vs. what XRIs must be evaluated as synonyms via local policy or resolution.

<marty>Who's to say? They syntax authors! The fact that the XDI TC was the first to come up with  that usage reinforces for me the need to do a better job of defining the syntax (and maybe even the semantics) then was done at the time the XDI TC came up with that usage. No slam intended - this is of course exactly what we're all trying to do.</marty> 

Here's a new question inspired by the examples in the previous messages.
Are the following equivalent?


[=Drummond] Again, by the current proposed normalization rule, none of the four XRIs above are equivalent. To begin with, they all state that the resource is being identified in a different global context, so that rules out syntactical equivalence. It would almost be like saying =drummond and @cordance*drummond should be syntactically equivalent. They might be proven to be synonyms in that they identify the same resource via resolution, yes, but to say anything about syntactical equivalence of identifiers that are not syntactically equivalent outside of a set of very narrow normalization rules is something I think we should avoid at all costs.

What determines which GCS to use? I think I'd favor having an xref
directly following a GCS character to be valid for only one of the GCS
characters (probably the $ or the +).


[=Drummond] Unfortunately that kind of special exception is antithetical to the concept of a simple, generalized syntax for XRIs. See my next message to the list regarding this point, as I believe it’s critical to coming to closure on XRI Syntax 2.1. 

<marty>Drummond, when you commented on my statement of preference, you did not attempt to answer the question; i.e., what determines which GCS to use?</marty>


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