RE: XRDS ref

["Drummond Reed" <drummond.reed@cordance.net>]

Wil & Gabe,

Here's my answer to Wil's original question: the ref attribute in the
outermost XRDS document: a) MUST be absolute, and b) is ALWAYS set by the
resolver (either a local resolver or a proxy) and never by the server. I
think of it as the resolver just "echoing back" the XRI it was asked to
resolve.

If a local resolver "hands off" resolution of a ref to another resolver, the
calling resolve should simple check that the value of the ref element on the
returned XRDS document is identical to what it asked for.

I agree that the ref attribute on the outermost XRDS document is primarily a
convenience -- it makes the document self-describing. However the role the
ref attribute plays in nested XRDS documents (those used to follow Refs) is
critical because it's the only place where the identifier for the root
authority MUST appear. In other words, because the first XRD in the nested
XRDS is relative to the root authority for the Ref XRI, it's <Query> is
going to contain a relative XRI subsegement like *foo. The only *required*
data that tells you that this is @*foo and not =*foo is the ref attribute on
the XRDS wrapper. (The ProviderID element in the first XRD identifies the
provider, but this element is not required, and furthermore it may be a
different identifier than the one used to identify the root authority.)

Wil, let us know if you have any other questions about this. I've made a
note in the WD11 Improvements section
(http://wiki.oasis-open.org/xri/Xri2Cd02/ResWorkingDraft11#head-7d258f97dc15
79a6f262bde09b98405ad86f69ec) to reflect what we've discussed here.

=Drummond 


-----Original Message-----
From: Gabe Wachob [mailto:gabe.wachob@amsoft.net] 
Sent: Monday, September 25, 2006 10:08 AM
To: 'Tan, William'; 'Drummond Reed'; 'Steve Churchill'; 'Chasen, Les'
Subject: RE: XRDS ref

I personally don't know what the point of the ref attribute is outside of
the recursive resolution (ie the XRDS which contains the results of
following a ref). And even then its just a sanity check.

I have been surprised to see the ref on out outer enclosing XRDS document...

	Gabe

> -----Original Message-----
> From: Tan, William [mailto:William.Tan@neustar.biz]
> Sent: Monday, September 25, 2006 5:37 AM
> To: Drummond Reed; Gabe Wachob; Steve Churchill; Chasen, Les
> Subject: XRDS ref
> 
> Hi guys,
> 
> It just occurred to me while writing the Perl resolver that there aren't
> any clear rules in WD10 about what a resolver should do when it sees the
> XRDS/@ref attribute.
> 
> If I understand correctly, the XRDS/@ref attribute is meant to contain an
> absolute XRI (though nothing in the spec says that it can't be a relative
> reference). An XRDS document returned by an authority resolution server
> may have the ref attribute set to a different absolute XRI than what was
> intended to resolve because the authority resolution server does not know
> who is pointing to it.
> 
> Should the resolver bother to sanity-check that value, or correlate that
> value with the contained XRDs?
> 
> I'm thinking the resolver shouldn't bother inspecting that value and only
> check the child XRD's.
> 
> I'm hoping someone could give a simple answer, otherwise we can move it to
> the wd11 open issues wiki.
> 
> 
> =wil (http://xri.net/=wil)
> 
> 
> p.s. I've checked in an early version of perl library that has a simple
> parser and resolver that uses xri.net. It took a few module namespace re-
> organization to get to the current naming conventions that I'm quite happy
> with. A full-blown direct resolver is being baked with whatever spare time
> I have.
> 
> http://openxri.cvs.sourceforge.net/openxri/perl-xri/
>