Re: [xri] Relative values in cross references

["Tan, William" <William.Tan@neustar.biz>]

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
>