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Subject: RE: [xri] Relative values in cross references
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 >
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