Re: [XRI] Back to XRI

Hi Stuart,

Thanks for the clarification.

I think it is clear that a combination of Link header and 303 will be  
required to communicate that the URI is about a "thing"  as David  
Booth puts it.

I personally prefer to be a "thing" as opposed to a "non-information  
resource",  or "abstract object".

With your help we are slowly making progress towards at-least  
understanding each other.

Regards
John Bradley


On 12-Sep-08, at 4:33 AM, Williams, Stuart (HP Labs, Bristol) wrote:

> Hello John,
>
>> -----Original Message-----
>> From: www-tag-request@w3.org [mailto:www-tag-request@w3.org]
>> On Behalf Of John Bradley
>> Sent: 11 September 2008 20:54
>> To: Booth, David (HP Software - Boston)
>> Cc: elharo@metalab.unc.edu; www-tag@w3.org
>> Subject: Re: [XRI] Back to XRI
>>
>> Thanks David,
>>
>> Certainly we want any http: subscheme to be completely
>> backwards compatible with existing agents.
>>
>> In the case of a XRI like =jbradley where the XRI is a
>> "identifier for an abstract object",  me in this case.
>> (Though thinking of myself as abstract still strikes me as a bit  
>> odd.)
>>
>> The question of what is returned when cast as a http: URI
>> becomes interesting.
>>
>> In conversation with TAG members using Link headers to point
>> at the URI for the XRDS meta-data seems reasonable.
>> We currently use a 302 redirect to point at some appropriate
>> html representation for compatibility reasons.  In my case a
>> contact page.
>>
>> Stuart Williams has pointed out that using a 303 redirect
>> would make it clear that the resource
>> http://xri.net/=jbradley itself is "an identifier for an
>> abstract object" and not a resource that has temporarily moved.
>
> Not quite... you not conclude that it *is* an identifier for an  
> abstract
> object, it may be but you cannot conclude that from the 303.
>
> What you can conclude (IMO), is:
>
> - that there is no claim (in the response) that the resource has  
> been moved
> to a new location (that's different from 301/302)
> - that you have not been returned a representation of the requested  
> resource
> (for undisclosed reasons)
> - that following the redirect (to something else) may yield relevant
> information *about* whatever http://xri.net/=jbradley refers to.
> - (probably) that the authority for http://xri.net/=jbradley in some  
> sense
> warrants there redirection as useful/relevant to the original request.
>
> The Link header approach (with GET or HEAD) is a mechanism that  
> would work
> similarly for both 'abstract' and 'concrete' resources in that it  
> provides a
> mechanism where a metadata reference can be provided alongside a
> representation in 200 response (indeed multiple references could be so
> provided).
>
> [snip the next bit if you want to stayout of the philosopical tarpit.]
>
> In the venacular of the TAG and the httpRange perma-thread  
> 'abstract' and
> 'concrete' correspond roughly to what have been called 'non- 
> information' and
> 'information' resources (but even muttering that risks another turn  
> of the
> wheel) - things that have mass (such as yourself) likely being
> 'non-information' resources (or 'abstract' as you say - and as you  
> say that
> seems odd). In fact in respect of the 'oddness' it would be  
> interesting to
> get some idea of bounds on where you think the boundaries are between
> abstractness and concreteness (though I suspect we will be no more
> successful with that than distinguishing information resources from
> non-information resources in a definitve way.
>
> From my pov... you are definitely *not* abstract, but there are many  
> facets
> to you some of which maybe (eg. your life, or life history)- though  
> I might
> wonder about say Shakespeare who has a similar concrete existence - no
> longer does - 'my notion of Shakespeare' is certainly abstract - but  
> if you
> and I are referring to Shakespeare are we referring to a concrete  
> thing or
> an abstract thing or... might we just not know or in many cases not  
> care to
> make a distinction?
>
> [If you really want to start making your head hurt there's an  
> interesting
> dialog about 3d/4d conceptualisation of the world recorded at [1]  
> and then
> its probably off to metaphysics 101... and probably a very long  
> pause...].
>
> [1] http://www.adampease.org/Articulate/dialog-3d-4d.html
>
>> The XRI TC originally selected the 302 redirect for
>> compatibility with pre http 1.1 browsers.
>> Changing to 303 redirects may brake some clients but it
>> unlikely to be a significant issue.
>>
>> I understand that some people will feel that using redirects
>> is inefficient,  however it seems the only way to communicate
>> the desired qualities of the identifier in http:
>
> What 303 does as opposed to 301/302 is make no assertion of  
> relocation of
> the reference resource. It simply says "See other".
>
> Whilst on the one hand that is a very weak claim, bearly more than a  
> hint
> that there *may* be useful related information elsewhere, it can be  
> used to
> useful effect.
>
> HTTP Link: headers with a more distinguished rel value could be used  
> to make
> a stronger claim (by virtue of what is entailed in the specification  
> of a
> given rel value eg. rel=http://xri.net/relations/xrds-metatdata  
> could be
> specified to be an assertion by the relevant (URI) authority that  
> related
> XRDS information *is* or at least *should be* available at the link  
> target.
>
>> This still allows XRI aware applications from directly
>> requesting the XRDS meta-data if they recognize the subscheme.
>>
>> I will also mention that some people seem to prefer the term
>> "http: profile" as a way to describe the qualities of a sub scheme.
>
> Personnally, I just see it as a way that some authority architects  
> the use
> of the URI subspace under its authority - be that *.xri.net or *.xri  
> (were
> that TLD to be sought).
>
> BTW: I'm sure that I spotted a URI of the form  something like
> library.hpl.hp.com.<service>.<otherdomain>.com which seem to suggest a
> similar pattern of use. Wish I'd been more careful to not thee  
> particular
> URI at the time.
>
>> Regards
>> John Bradley
>
> --
> Hewlett-Packard Limited registered Office: Cain Road, Bracknell,  
> Berks RG12
> 1HN
> Registered No: 690597 England