RE: [xri] Relative values in cross references

["Schleiff, Marty" <marty.schleiff@boeing.com>]

I don't really like the idea of relative XRIs and/or URIs in a cross
reference (even though I can think of a use case). The only way I can
even make sense of the concept is to recognize that "the value of a
cross reference is interpretted within the context of the cross
reference's parent" as Wil pointed out. So, if we're going to support
relative XRIs in cross references, I think we should support relative
URIs too.  


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

-----Original Message-----
From: Tan, William [mailto:William.Tan@neustar.biz] 
Sent: Monday, April 09, 2007 1:45 PM
To: Drummond Reed
Cc: Schleiff, Marty; xri@lists.oasis-open.org
Subject: Re: [xri] Relative values in cross references

Relative URI references are less structured than XRI ones. While a
relative URI may pass the ABNF test for a relative XRI, it is fairly
coincidental. We can't guarantee that all relative URIs are also
relative XRIs.

However, from a syntax point of view, all we really care is that the
value inside a cross reference nest properly, i.e. if there are opening
parentheses, that they are matched by the same number of closing
parentheses in the right order.

Since the value of a cross reference is interpreted within the context
of the cross reference's parent, do we really need to dictate its
content?

=wil

Drummond Reed wrote:
>
> Marty,
>
> Good question. When the TC discussed this question back in XRI 2.0, we

> concluded that parenthetical cross-references are fundamentally a way 
> of supporting polyarchical identifiers (identifiers that cross 
> hierarchies), and since both absolute and relative identifiers can be 
> polyarchical, we wanted to support both forms.
>
> The challenge we had was that for parsing purposes it needs to be 
> unambiguous whether a parenthetical cross-reference is an XRI or a 
> URI. In absolute form that's easy, but no so in relative form because 
> neither a relative XRI or a relative URI can contain a scheme name.
> Since in XRIs the "native" form is XRI, we concluded our only option 
> was to accept relative XRIs and not relative URIs.
>
> However this end out being an almost immaterial restriction because, 
> unlike absolute URIs, the vast majority of relative URIs are in fact 
> valid relative XRIs. (In fact it's hard to think of one that's not.) 
> So effectively, there is no difference.
>
> Hope this helps,
>
> =Drummond
>
> ----------------------------------------------------------------------
> --
>
> *From:* Schleiff, Marty [mailto:marty.schleiff@boeing.com]
> *Sent:* Monday, April 09, 2007 8:43 AM
> *To:* xri@lists.oasis-open.org
> *Subject:* [xri] Relative values in cross references
>
> Hi All,
>
> In looking through the archives for some other stuff, I encountered 
> discussion about relative cross-references 
> (http://www.oasis-open.org/archives/xri/200309/msg00035.html). At some

> point I may wish to re-visit the logic/conclusions in that thread, but

> for now I just want to ask a new question:
>
> Does it make sense to allow relative XRIs in a cross reference, but 
> not relative URIs? I mean, aside from any syntax challenges in 
> representing the difference.
>
> Marty.Schleiff@boeing.com <mailto:Marty.Schleiff@boeing.com>; CISSP 
> Associate Technical Fellow - Cyber Identity Specialist Computing 
> Security Infrastructure
> (206) 679-5933
>