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Subject: RE: [xri] Difference between global and local subsegments (was RE: [xri] Increased complexity in resolver.)
Steve, Perhaps there was some misunderstanding. The
resolution flows I depict always “honor sticky stars”. What I was
pointing out is that it is up to the local policy of the XRI authority
answering a resolution request for a global-xref as to how it determines its
response. In other words, in resolving
@ootao+west*steve, @ootao is queried for the global xref “+west*steve”.
@ootao will *always* answer this
request with a single XRDS document containing a single XRD for “+west*steve”.
The only question is how @ootao will
figure out its response. One obvious choice is to just register “+west*steve”
directly and serve up the XRD for it. Another choice would be for @ootao to *internally* (invisibly to the original
resolution request) query itself for +west, then query @ootao+west for *steve,
THEN return the response to the original resolver. And as Marty points out, yet another
choice would be for @ootao to query ANOTHER external authority that it
recognizes as the authority for “+west”, and then based on that
response query @ootao+west for *steve, and then return the response to the
original resolver. Hope this helps, =Drummond From: Steven Churchill
[mailto:steven.churchill@xdi.org] Drummond, See my single comment in ###. ~ Steve From: Drummond Reed
[mailto:drummond.reed@cordance.net] Steve, Marty, Bill, et al: It’s Sunday night, and after
thinking about Steve’s observation over the last few days, I’ve
come to a greater appreciation of the difference between global and local
subsegments in an XRI authority segment. (Note that by “global
subsegment” I mean the global-literal and global-xref rules on http://wiki.oasis-open.org/xri/XriCd02/XriAbnf2dot1,
and by “local subsegment” I mean the local-literal and local-xref
rules on that page.) First, in XRI 2.0, an XRI authority
segment consisted of only one global subsegment. It could contain any number of
local subsegments inside it (and those could be either local-literals or
local-xrefs), but it could not contain another global subsegment. In the proposed XRI 2.1 syntax, an XRI
authority segment can contain more than one global subsegment. So what Steve noticed is that while the
XRI resolution rules are the same for both 2.0 and 2.1, i.e., that a resolver
just “walks the tree” of top-level subsegments in an XRI authority
segment to resolve it, that tree of subsegments has one important structural
difference: once you hit the first global-xref, every other top-level
subsegment must be a global-xref. In other words, think of the pattern this
way: 1) XRI authority segments in XRI 2.0 (with
the exception of cross-reference root authorities):
GCS-char
local local
local …
/ 2) XRI authority segments in XRI 2.1:
GCS-char
local local
local …
global global global
… / I think this makes it easier to see that
when you “switch over” from resolving local subsegments to
resolving global subsegments, each global subsegment is relative to the
previous one just like each local subsegment is relative to the previous one. Secondly, when you apply that to Steve’s
example – of resolving @ootao*west*steve and @ootao+west*steve,
it’s true that the first one parses into four top-level
subsegments…
@
ootao
*west
*steve …and the second one into
three…
@
ootao
+west*steve However, if the policy of @ootao is that
*west and +west are synonyms, then @ootao*west can delegate to *steve and the
same delegation can be recognized for @ootao+west*steve. Here’s the flow: @ootao*west*steve 1) Resolver queries @ for ootao 2) @ responds for ootao 3) Resolver queries @ootao for *west 4) @ootao responds for @ootao*west 5) Resolver queries @ootao*west for *steve 6) @ootao*west responds for
@ootao*west*steve @ootao+west*steve 1) Resolver queries @ for ootao 2) @ responds for ootao 3) Resolver queries @ootao for +west*steve 4) @ootao queries @ootao+west for *steve 5) @ootao+west responds for
@ootao+west*steve 6) @ootao responds @ootao+west*steve ### If you follow this to its logical
conclusion, it nets out as: it is left to the policy of the authority
resolution service as to whether or not it honors sticky stars. Allowing a
compliant authority resolution service this type of flexibility will lead to
massive interop problems. Notice that it takes the same number of
steps, for the same number of delegations, however @ootao is responsible for
answering the +west*steve response, vs. the original client resolver being
responsible for resolving it. This ability to control who will provide
the resolution response is, I believe, one of those key guidelines Marty is
looking for (and which I am indeed tasked to elucidate) as to whether an XRI
author should use local subsegments or global subsegments. =Drummond (Note: I’m headed off
early tomorrow morning for the Higgins f2f meeting in From: Steven Churchill
[mailto:steven.churchill@xdi.org] > I know that Steve and I lost the
"direct concatenization" vs. "compact syntax" vote, but I'd
just > like to point out that under compact
syntax "@ootao+west" normalizes to
"@ootao*(+west)". > And if "@ootao*west"
and "@ootao+west" are declared as synonyms, then you could logically > deduce that
"@ootao*west*steve" and "@ootao*(+west)*steve" are
synonyms. I agree. I’d just like to point out
that the way that the two would be “declared as synonyms” is that
“*(+west)” would be added as a local synonym to
“*west”. ~ Steve From: Schleiff, Marty
[mailto:marty.schleiff@boeing.com] Hi Bill & Steve (& All), I think Steve meant that EVEN IF
"@ootao*west" and "@ootao+west" are declared as synonyms,
then "@ootao*west*steve" and "@ootao+west*steve" are not
synonyms (unless they are explicitly declared as synonyms). I know that Steve and I lost the
"direct concatenization" vs. "compact syntax" vote, but I'd
just like to point out that under compact syntax
"@ootao+west" normalizes to
"@ootao*(+west)". And if "@ootao*west" and
"@ootao+west" are declared as synonyms, then you could logically
deduce that "@ootao*west*steve" and "@ootao*(+west)*steve"
are synonyms. Marty.Schleiff@boeing.com; CISSP
From: Barnhill,
William [mailto:barnhill_william@bah.com] Hi all, |
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