RE: Perisistence (was RE: [XRI] Private naming conventions and hypermedia)

Hello John,



  _____

From: John Bradley [mailto:john.bradley@wingaa.com]
Sent: 08 August 2008 00:48
To: Williams, Stuart (HP Labs, Bristol)
Cc: Mark Baker; Henry S. Thompson; www-tag@w3.org
Subject: Re: Perisistence (was RE: [XRI] Private naming conventions and
hypermedia)


Hi Stuart,

Reply inline.

On 7-Aug-08, at 2:57 AM, Williams, Stuart (HP Labs, Bristol) wrote:


 <snip/>


This must be an identifier for which the parent authority is the final
authority.


For any XRI other than a community root authority (DNS) the CID must consist
of the parent authorities CanonicalID plus one additional subsegment.


Once assigned, a parent authority SHOULD NEVER
a) change or reassign a CanonicalID value


Never change => only ever assign one CID to a given thing?



 <snip/>

Assuming that that's out of the way, back to what it is that is persistent.

Your response to my question on that was:



B)  is the closest.  It is the mapping assigned by the parent


authority to the relationship between and administrative


authority and  the identifier.



where B) was



b) The association between the identifier and whatever it refers to (a


resource?)?



I think this in part gets close to the heart of the matter. What I believe
you are saying is that what it is that is persistent is, as you say, the
relationship between an (persistent) identifier and the authority that
administers it.



Yes it is an administrative relationship.
! segments are used to specify persistent identifiers―identifiers that are
permanently assigned to a resource and will not be reassigned at a future
date.

In this context the resource is the XRD document.  The administrative
control of that XRD document must not be reassigned.


Ah... we're back into the data v metadata thing. In what I wrote I was
meaning the resource to be whatever the XRI was intended to be used to refer
to (denote), rather than metadata (an XRD document) about that thing. eg. in
the example I tried to construct earlier of an XRI for the "XRI 2.0
Resolution Spec" the resource would be just that, the spec, and not the XRD
document which (one presumes) would describe the spec. (or at least how to
obtain a copy of it).

>From your answer above, what is persistent is the relationship between and
XRD 'resolved' by the resolution protocol and the administrative authority
that controls that document. As the content of the XRD document itself can
change, and could presumably over time described different things (maybe)
then the relationship between a persistent XRI and the thing it denotes
could change by fiat of a change in an XRD... though that may be a violation
of XRI architecture which might demand a fresh persistent XRI CID in such a
circumstance - which then breaks the premise (because we have a new CID and
a new persistent relationship).



If =skw is assigned to you along with =!BF81.FD97.C81B.B4E5 and at some
point you stop paying for =skw and TBL wants to purchase it he can get =skw
but not =!BF81.FD97.C81B.B4E5,  a new CID would be created if he needed it.


As the openid.claimed_id is the CID and not the iName TBL would not be able
to get access to your resources.


It is always possible to reassign the administrative control of a XRD to
some other entity if the owner requests it.
That might be necessary if a company is sold or something like that.



This is largely a social matter wrt to administrative policy rather than a
technical one. The underlying social issue that this seeks to address is a
lack of stabilty in this relationship induced by the administrative policies
assoicated with the DNS - specifically, that the authority for a given
domain name can change over time. If DNS domains were not 'rented' on a 1-2
year renewal basis where an authority can 'accidentally' loose
administrative control over the name through inattention, or simply
relinquish control which is subsequently picked up by another party.

Is that the primary issues that motivates persistent (top-level) XRI path
names?



Yes DNS has no way to detect identifier recycling.


That's a pity.



<snip/>





Anyway, the persistence XRI speaks of for persistent identifiers is the
persistent in the relationship between and identifier and its administrative
authority.





Yes,  the identifier is assigned to a XRD and the administrative authority
for that XRD will not be reassigned.


There's that data/metadata thing again...  we (or I) need to have a
consistent understanding of what an XRI is assigned to, AIUI, an XRD(S)
document arising as part of the resolution process is a stepping stone in
making that determination, but in general is *not* what is denoted or
referred to by the identifier being resolved. I think that there may be a
further obligation on the administrative authority not to change *what* is
being described in an XRD(S) document without assigning a new CID.



By contrast a reassignable XRI can be assigned by an identifier authority to
represent a different resource at some future time.


I hope that helps.


Best Regards
John Bradley
OASIS IDTRUST-SC
http://xri.net/=jbradley
五里霧中

<snip/>

Regards

Stuart
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