W3C home > Mailing lists > Public > www-tag@w3.org > September 2008

Re: Cool URIs don't change? Was Re: Perisistence

From: John Bradley <john.bradley@wingaa.com>
Date: Mon, 15 Sep 2008 13:15:22 -0700
Cc: "Williams, Stuart (HP Labs, Bristol)" <skw@hp.com>, Mark Baker <distobj@acm.org>, "www-tag@w3.org" <www-tag@w3.org>
Message-Id: <0CFB37C0-B9A9-48BC-BE09-F910307D5AA2@wingaa.com>
To: ht@inf.ed.ac.uk (Henry S. Thompson)
Hi Henry,

My comments are inline.

On 15-Sep-08, at 11:38 AM, Henry S. Thompson wrote:

> Hash: SHA1
> I've been re-reading this tangled thread, and want to pull out one
> tiny bit to test my understanding:
> John Bradley wrote:
>> 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.
> Would I be correct in saying that it's because you feel obliged to
> acknowledge that the injunction "Cool URIs don't change" is
> unrealistic, indeed that it you allow naming authorities to recycle  
> names
> under their control, e.g. after non-payment of annual rental fees,
> that the corresponding URIs _will_ change, that you then need to
> make a distinction between what you call persistent vs. non-persistent
> URIs?  That is, a ! is the way a naming authority indicates that it
> will _not_ recycle a name.

True however XRI predates the Cool URIs document.
It is possible that Purl in combination with Cool URIs start to  
approach the XRI persistence functionality.

The ! symbol indicates that the naming authority will not recycle the  

However without some sort of sub-scheme as David Booth and I have  
referred to there is no way by inspection to determine if a http: URI  
is persistent.

> Would I furthermore be correct in concluding that it follows that if a
> naming authority leases a _persistent_ name to someone, and they stop
> paying, that all the naming authority is committed to doing is
> retiring the name and never re-issuing it?  It continues to identify
> what it always did, in principle at least, although in practice it may
> not (will definitely not?) be possible to retrieve either metadata or
> representations using it.

The authority may continue to express a XRDS document,  however that  
document would not contain information beyond what the Canonical  
Identifier for the XRDS is.

XRI resolution only returns meta-data so returning a representation is  
a function http: or other protocol specified in the XRDS.

> And that the guarantee that a persistent name always identifies the
> same resource depends on the good behaviour of the leasee of that
> name?

The issuing authority's good behavior is required.  There is a IANA  
like process for registrars to help guarantee that.
For community registries like @boeing ,  they are responsible for  
there own good behavior.

> And finally, that persistence does _not_ imply continuity of
> ownership?  That is, I may lease a persistent name from some naming
> authority, and then sell that name on to someone else.  It's then up
> to _their_ good behaviour to continue to use that name to identify the
> same resource.
In general people sell and transfer reassignable identifiers like  

You need to make special provisions to transfer a non-reassignable  
identifier like =!BF81.FD97.C81B.B4E5

You need to make a case to the registrar that the entity controlling  
the identifier has been purchased and it is going to continue to be  
used to identify the same "non-information resource".

The path of least resistance for people is to just get a new non- 
reassignable identifier to map the reasonable one to.

Remember XRI has an extra level of indirection to facilitate the  
polymorphic relationship between "non-information resource locators"  
and the canonical identifier of a "non-information resource".

This last is a subtle but important difference when you consider XRI  
meta-data discovery vs http: locator resolution.

I hope this helps clarify XRI persistence.

John Bradley
> Thanks,
> ht
> - --
>       Henry S. Thompson, School of Informatics, University of  
> Edinburgh
>                         Half-time member of W3C Team
>      10 Crichton Street, Edinburgh EH8 9AB, SCOTLAND -- (44) 131  
> 650-4440
>                Fax: (44) 131 651-1426, e-mail: ht@inf.ed.ac.uk
>                       URL: http://www.ltg.ed.ac.uk/~ht/
> [mail really from me _always_ has this .sig -- mail without it is  
> forged spam]
> Version: GnuPG v1.2.6 (GNU/Linux)
> iD8DBQFIzquLkjnJixAXWBoRAqdIAJ98y0Fb4etcXClieDe7SbT5pw9mbgCgg85p
> J6xjGBNd8SXHdi+PcoFd/BU=
> =b99e

Received on Monday, 15 September 2008 20:16:04 UTC

This archive was generated by hypermail 2.3.1 : Wednesday, 7 January 2015 15:32:58 UTC