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Subject: RE: [xri] A different perspective on * and / (long)


Drummond-
	Somewhere along the line, I'm failing to connect the dots. While I understand the idea that peer-links should be representable in XRIs, and I understand your proposal of using syntax to do this, I'm not understanding how this impacts the */: vs. *:/*. discussion..

	-Gabe (who never admits to things he thinks about at 4am ;-)

 
__________________________________________________ 
gwachob@visa.com
Chief Systems Architect
Technology Strategies and Standards
Visa International 
Phone: +1.650.432.3696   Fax: +1.650.554.6817


> -----Original Message-----
> From: Drummond Reed [mailto:drummond.reed@cordance.net]
> Sent: Friday, June 11, 2004 9:10 AM
> To: xri@lists.oasis-open.org
> Subject: [xri] A different perspective on * and / (long)
> 
> 
> I realize I am in the minority in the perspective I'm sharing 
> on the * vs. :
> issue. In the message below Peter adds his vote along with Gabe, Mike,
> Loren, and Dave to the preference to use both * and : as "second-level
> hierarchy characters", whereas I am advocating using just *.
> 
> However after a conversation Dave and I had about this late 
> yesterday, I
> woke up thinking about it at 4am this morning and came to a 
> much deeper
> understanding of why there appears to be such a huge gap 
> between these two
> perspectives. Since I couldn't get back to sleep, I'll try to 
> explain it
> here.
> 
> First, just to make it clear, I agree with everyone that if 
> the choice is
> simply between the "readability" of the two examples given 
> below, i.e.:
> 
> xri:@:3*:4*:5/:6*:7
> or
> xri:@:3:4:5/:6:7
> 
> ...then of course it appears to be a no-brainer. The latter 
> is more compact
> and, as Peter says, "much easier to read".
> 
> But therein lies the issue. What is "easier to read" depends 
> on what you are
> reading for. What I realized laying in bed at 4am this 
> morning is that I am
> reading for something entirely different. But to explain this requires
> explaining the entire worldview behind this perspective, and entire
> worldviews are not easy to explain, so please bear with me 
> while I try.
> 
> In this second worldview, * would not be considered a 
> "secondary hierarchy
> character", but an "alternative hierarchy character" on an 
> equal footing
> with slash. 
> 
> I can just hear Dave screaming right now, "What does Drummond 
> mean, 'an
> "alternative hierarchy character" on an equal footing with 
> slash'?? How
> could there be such a thing? Slash is THE 2396 hierarchy character! It
> defines 2396 segments. The only option we have is to define 
> subsegments
> within slash segments!"
> 
> But this is exactly what I mean about two entirely different 
> worldviews. In
> the 2396 worldview the world is purely hierarchical. There is 
> only slash
> because there is only hierarchy.
> 
> It's pretty ironic, then, that URIs based on 2396 are the 
> very basis of the
> World Wide Web, which is the very opposite of hierarchy. It's 
> a peer-to-peer
> web. Any page can link to any page.
> 
> Laying in bed at 4am, I did the following thought experiment, "Using
> conventional URIs, is there any way you can address the LINK 
> between two web
> pages?" In other words, not the URI of Page A or the URI of 
> Page B, but the
> LINK from Page A to Page B. Literally, the A tag present in 
> the HTML of Page
> A that links to Page B.
> 
> There is certainly no standard way, at least that I know of. 
> So I started
> thinking through how you would do it. If Page A was expressed 
> as XHTML, then
> the actual node of the XHTML document that contains the link 
> to Page B would
> at least be addressable using an XPath expression under the 
> URI of Page A.
> So you could have something like:
> 
> http://www.example.com/Page-A#Xpath-to-A-tag-linking-Page-B
> 
> Of course, there is no spec for doing this that I am aware 
> of. However it
> wouldn't be hard to construct one. Since you know the link is 
> in an A tag,
> you'd just need a standard XPath query that says, "Give me 
> the A tag whose
> HREF attribute equals the following value" and then supply 
> the target URI as
> a paremeter. Say this query was called "Xpath-A-ref". Then 
> any site that
> supported this query could resolve a URI that looked like the 
> following:
> 
> http://www.example.com/Page-A?Xpath-A-ref&HREF="http://www.sit
> e.com/Page-B" 
> 
> Such an address would actually let you address Page B in the 
> context of Page
> A. It lets you construct a path ACROSS pages, not just DOWN 
> the DNS tree and
> local file path hierarchy to a specific page.
> 
> Why would you want to be able to address across Web pages? If 
> you wanted to
> be able to follow the path of who is linked to who. It lets you test
> assertions about relationships between pages. If the address 
> above resolves,
> it tells you Page A is linked to Page B. If it doesn't, they aren't.
> 
> Now, imagine if there was: a) a standard URI syntax character 
> that equates
> to the link query operation "?x-path-A-ref" above, and b) a 
> standard way in
> URI syntax to nest one URI inside another. Let's say the 
> standard link query
> character was * and the nesting syntax was to enclose the 
> nested URI in
> parentheses. Then the URI above could be expressed much more 
> compactly and
> readably as:
> 
> 	http://www.example.com/Page-A*(http://www.site.com/Page-B) 
> 
> Now let's take one more step. Say that the author of Page A 
> had his own name
> for Page B inside the HREF tag that points to 
> "http://www.site.com/Page-B";.
> Say this name was "Glockenspiel". This is really a relative 
> identifier for
> Page B, since it's relative to the Web page 
> http://www.example.com/Page-A.
> But in the context of this Web page, it's very likely to be 
> unique, since
> the author of Page A is unlikely to create two outgoing links 
> to different
> resources on the same Web page and label both the A tags identically. 
> 
> In this case there is a second way to address the link 
> between Page A and
> Page B using this relative identifier. This would look like:
> 
> 	http://www.example.com/Page-A*(Glockenspiel) 
> 
> I know this example has been quite extensive, but as you can 
> see, the point
> is that in this alternative worldview - this Web-based worldview -
> peer-to-peer linking relationships have an equal status with 
> hierarchical
> relationships. Neither is "good" or "bad". Neither is "primary" or
> "secondary". They are simply equally valid. Like Cartesian and radian
> coordinate systems, they both let you address any point on a 
> plane - it's
> just that each one can be much more appropriate for certain tasks.
> 
> It follows then that in this worldview, the primary failing 
> of 2396 syntax
> is that it does not accommodate the peer-to-peer linking 
> worldview. It only
> accommodates the hierarchical worldview. It has no syntax for 
> addressing
> link relationships, nor for nesting identifiers for this 
> purpose (i.e.,
> cross-references). In syntactic terms, it has only /, and no * nor ().
> 
> Those of you who know me know why I am so passionate about 
> this subject. To
> get from the Web to the Dataweb, we must be able to express the links
> between data and the links between data sharing authorities. 
> Suddenly it is
> as important (if not more important) to be able to address 
> the source of
> authority and permission in a data sharing relationship as it 
> is to be able
> to address the data being shared.
> 
> For example, look at the following sample XRI:
> 
> xri:xri-A/(xri-B)*(/($contract)/this-contract/($v1))*(/(+email
> )/work/($v2))
> 
> (Note that the values "xri-A" and "xri-B" are placeholders 
> for the actual
> XRIs for Authority A and Authority B, and "$contract" is the 
> proposed XRI
> service dictionary identifier for XDI link contracts.) This 
> is from a thread
> about potential XDI contract addressing available at
> http://wiki.idcommons.net/moin.cgi/DataSharing#head-0bd5430345
> 33c5641c0beacf
> 65be418a7a9c7fc5. 
> 
> Although this particular example is in the context of XDI 
> (and uses only a
> proposed addressing syntax in that context), what I believe 
> it illustrates
> is the tremendous importance, in that context, of link 
> relationships. For
> example, this XRI expresses that authority A's relationship 
> with authority B
> (xri-A/xri-B) is linked to a link contract from authority A
> (/($contract)/this-contract/($v1)) which is linked to a 
> specific item of
> data from authority A (/(+email)/work/($v2)).
> 
> So, in conclusion:
> 
> * In the hierarchical-only worldview, / reigns supreme, and 
> therefore the
> distinction between * and : as "secondary hierarchy" 
> characters appears
> relatively minor.
> 
> * In the combined hierarchy-and-peer-to-peer-link worldviews, 
> / and * are
> equally important and equally valid first-level delimiters. / 
> is used to
> express for hierarchical relationships between resources and 
> * is used to
> express peer-to-peer linking relationships between resources. In this
> worldview, both "/:" and "*:" would be equally valid, as 
> colon would always
> be used as the prefix for a persistent identifier.
> 
> I believe this worldview is not unique to XDI. Although XDI 
> architecture is
> fundamentally based on the ability to express links between 
> resources, and
> it uses XRIs for this purpose, I believe that establishing 
> the syntactic
> "equal footing" of * and / for the purpose of enabling the 
> expression of
> peer-to-peer linking vs. hierarchical relationships could 
> apply to many
> other uses of XRI beyond the scope of XDI.
> 
> I hope this explanation helps bridge the gap between these 
> two worldviews.
> 
> =Drummond 
> 
> -----Original Message-----
> From: Peter C Davis [mailto:peter.davis@neustar.biz] 
> Sent: Friday, June 11, 2004 5:45 AM
> To: Lindelsee, Mike
> Cc: xri@lists.oasis-open.org
> Subject: RE: [xri] RE: Single delegation character
> 
> ditto.  it is, among other things, much easier to read.
> 
> --- peterd
> 
> On Thu, 2004-06-10 at 17:56, Lindelsee, Mike wrote:
> > I also prefer the latter for the same reasons that Dave and 
> Loren do.
> > 
> > Mike
> > 
> > -----Original Message-----
> > From: Dave McAlpin [mailto:Dave.McAlpin@epok.net]
> > Sent: Thursday, June 10, 2004 2:26 PM
> > To: Loren West; xri@lists.oasis-open.org
> > Subject: RE: [xri] RE: Single delegation character
> > 
> > 
> > Good point. Now that we've beaten the delegation issue to 
> death, we can
> > come back to the original question about whether we should 
> define one or
> > two second level delimiters.
> > 
> > The question is whether we prefer
> > 
> > xri:@:3*:4*:5/*:6*:7
> > 
> > or
> > 
> > xri:@:3:4:5/:6:7
> > 
> > for reasons already stated. My preference is the second, 
> i.e. to define
> > two second level separators, star ("*") and colon (":").
> > 
> > Dave
> > 
> 
> 
> 
> 
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