Re: [urn] Fragments Re: I-D Action: draft-ietf-urnbis-rfc2141bis-urn-02.txt

Leslie Daigle <leslie@thinkingcat.com> Tue, 27 March 2012 15:38 UTC

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Subject: Re: [urn] Fragments Re: I-D Action: draft-ietf-urnbis-rfc2141bis-urn-02.txt
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Hi Martin,

In-line...


On 3/26/12 3:25 AM, "Martin J. Dürst" wrote:
> Hello Leslie,
>
> On 2012/03/25 22:00, Leslie Daigle wrote:
>>
>> Hi,
>>
>> I am having troubles reconciling this use of fragments with RFC3986, the
>> URI syntax document.
>>
>> My understanding of RFC3986 suggests that fragments are strictly and
>> uniquely tied to media, and thus would be applied to the results of a
>> URN resolution, irrespective of namespace.
>>
>> So, if you have <urn>#<fragment>, you resolve <urn> and apply <fragment>
>> in whatever way makes sense for the media type of what you got back.
>>
>> The issue with doing that with URNs is: they are designed to be flexible
>> enough to support multiple types of response -- the URN does not
>> designate a type.
>>
>> For example, you might get a PDF back instead of HTML, and then your
>> HTML #<fragment> will be pointless.
>>
>> Even if you say (as the document currently does) that fragments are
>> allowed only on a per-namespace basis, I am concerned that the resulting
>> URN namespaces would have to be severely limited in terms of URN
>> functionality: you are essentially saying that those namespaces must be
>> architected such that they only ever return single media type responses,
>> or responses for which the fragments will make sense across all
>> supported types.
>
> Could this be relaxed to "responses for which there is a commitment that
> the fragments, if interpretable, are interpreted consistenly"? This
> would not exclude media types where a fragment identifier doesn't make
> sense, but would, if implemented diligently, produce consistency across
> all those media types where fragment identifiers make sense.

I'm really not sure what this means, in practice.

And, I find myself wondering:  what's the _specified_ behaviour when a 
fragment reference cannot be resolved (by the client)?

Leslie.

>
> Regards, Martin.
>
>
>> That is very constraining on the namespace, and the use
>> of URNs, IMO.
>>
>> For myself, this doesn't make the case that the URN syntax can be
>> updated to allow the use of fragment identifiers.
>>
>> And, if the consensus winds up being that this does make the case to
>> allow that, I would further argue that the text describing the
>> per-namespace use considerations would need
>>
>> 1/ a very thorough review by URI experts to make sure it actually would
>> hold water,
>>
>> 2/ to be clear about the constraints it puts on the overall URN
>> namespace in question
>>
>> 3/ to be in a separate document all on its own, because it is severely
>> distracting from a document that is meant to be the description of the
>> syntax of URNs in general.
>>
>> Leslie.
>>
>>
>>
>> On 3/11/12 9:05 PM, internet-drafts@ietf.org wrote:
>>>
>>> A New Internet-Draft is available from the on-line Internet-Drafts
>>> directories. This draft is a work item of the Uniform Resource Names,
>>> Revised Working Group of the IETF.
>>>
>>> Title : Uniform Resource Name (URN) Syntax
>>> Author(s) : Alfred Hoenes
>>> Filename : draft-ietf-urnbis-rfc2141bis-urn-02.txt
>>> Pages : 32
>>> Date : 2012-03-11
>>>
>>> Uniform Resource Names (URNs) are intended to serve as persistent,
>>> location-independent, resource identifiers. This document serves as
>>> the foundation of the 'urn' URI Scheme according to RFC 3986 and sets
>>> forward the canonical syntax for URNs, which subdivides URNs into
>>> "namespaces". A discussion of both existing legacy and new
>>> namespaces and requirements for URN presentation and transmission are
>>> presented. Finally, there is a discussion of URN equivalence and how
>>> to determine it. This document supersedes RFC 2141.
>>>
>>> The requirements and procedures for URN Namespace registration
>>> documents are set forth in BCP 66, for which RFC 3406bis is the
>>> companion revised specification document replacing RFC 3406.
>>>
>>>
>>> A URL for this Internet-Draft is:
>>> http://www.ietf.org/internet-drafts/draft-ietf-urnbis-rfc2141bis-urn-02.txt
>>>
>>>
>>>
>>> Internet-Drafts are also available by anonymous FTP at:
>>> ftp://ftp.ietf.org/internet-drafts/
>>>
>>> This Internet-Draft can be retrieved at:
>>> ftp://ftp.ietf.org/internet-drafts/draft-ietf-urnbis-rfc2141bis-urn-02.txt
>>>
>>>
>>>
>>> _______________________________________________
>>> urn mailing list
>>> urn@ietf.org
>>> https://www.ietf.org/mailman/listinfo/urn
>>
>

-- 

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"Reality:
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Leslie Daigle
leslie@thinkingcat.com
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