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Subject: RE: [xdi] XDI/XRI Question

Coming in Sunday night after being offline at RSA the last few days of last
week, I'm afraid I have some catching up to do in this thread. Let me just
observe that Dave is correct that both of the following XRIs are
syntactically legal:


Fen is also correct that there is a proposal that all reassignable XRIs
registered in the =, @, and + spaces be treated as cross-references in order
to allow greater expressiveness in human-friendly global XRIs. However that
proposal affects only how such XRIs would be intepreted at the presentation
layer and not the machine-level syntax.

So as long as we are talking machine-level syntax, the above two XRIs are
both legal but not equivalent. The first one is using the chars "=" and "+"
as relative identifiers under the @epok.pin authority. The latter is using
cross-references to global identifiers registered under the = and +
authorities. This approach explicitly allows such identifiers to be shared
across domains for the purposes of establishing logical, cross-domain
equivalence of resources, which I think was what Bill was first asking
about, but now I've got to go back and better understand his original


-----Original Message-----
From: Dave McAlpin [mailto:dave.mcalpin@epok.net]
Sent: Sunday, February 29, 2004 4:12 PM
To: 'Fen Labalme'; 'Dave McAlpin'; drummond.reed@cordance.net
Cc: xdi@lists.oasis-open.org; xri@lists.oasis-open.org
Subject: RE: [xdi] XDI/XRI Question

First, I'll acknowledge that xri:@epok.pin/=Dave/+email is syntactically
legal. Second, because =Dave/+email is part of local access and is therefore
outside of the define resolution protocol, it's conceivable that it could be
considered equivalent to (=Dave)/(+email). Having said that, I think it's
reflects a very bad practice. I much prefer xri:@epok.pin/(=Dave)/(+email).
The reason a subsegment is allowed to start with =, + or @ is because it's
not ambiguous with a fully qualified XRI. In other words, =Dave is allowed
because = couldn't possibly be a global context symbol - if it were, it
would be inside a cross-reference. Equating the two is wrong, in my opinion.
Drummond may disagree.


> -----Original Message-----
> From: Fen Labalme [mailto:fen@idcommons.org]
> Sent: Sunday, February 29, 2004 12:57 AM
> To: Dave McAlpin; drummond.reed@cordance.net
> Cc: xdi@lists.oasis-open.org; xri@lists.oasis-open.org
> Subject: Re: [xdi] XDI/XRI Question
> "Dave McAlpin" <dave.mcalpin@epok.net> writes:
> > This is an edited version of an email thread from Bill. I haven't had
> > time to respond, but I'll try to put something together this weekend
> > unless someone else chimes in first.
> ...
> > I'm thinking the resolution would go like this?
> >
> >     Original XRI:   xri:@epok.email.(@epok.pin.(=Dave))
> I think the original XRI could look like this:
>                       xri:@epok.pin/=Dave/+email
> If I understand the gist of recent discussions with Drummond, this could
> be equivalent (if real world resolver best practices so dictate) to:
>                       xri:@(epok.pin)/(=Dave)/(+email)
> This would look up =Dave according to the epok.pin authority, and then
> look up the +email element within that object.
> > A few other questions:
> >
> > 1) The xri form I'm looking for was something that could be put on a
> > biz card and the email would be good even if you transferred jobs,
> > assuming you updated a registry. Is there a form for that? I saw
> > electronic business cards as one example use case, but has the syntax
> > for that use been developed?
> A shorthand that might be useful for business cards might be something
> like this:
>                       xri: epok =Dave +email
> where the resolver inserts slashes between the segments.
> While this XRI is totally local to Epok, and therefore would not follow a
> person as they changed jobs, simply removing the company name would find
> Dave (assuming he had a global e-name).  Note that when =Dave is
> resolved with respect to a company's authority, +email may resolve to a
> different value than when looked up via the global name.  Also, link
> contracts prevent =Dave from being directly spammed.
> I'm not sure if any of this is correct, but I'm trying to learn this
> stuff and figure I'd try to get my thoughts out there.
> Best,
> Fen
> PS: Email problems:
> I replied to Bill Thursday night, but my email to the list went into a
> black hole and never appeared on the XDI list.  I've sent an email to
> Scott McGrath about this, and hopefully this one will be distributed.
> My original note (already out-of-date) is attached.

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