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Use Cases [Was Re: I-D ACTION:draft-nottingham-http-link-header-01.txt]

From: Harry Halpin <hhalpin@ibiblio.org>
Date: Thu, 20 Mar 2008 16:36:41 -0400
Message-ID: <47E2CAD9.9060101@ibiblio.org>
To: Alan Ruttenberg <alanruttenberg@gmail.com>
Cc: Phil Archer <parcher@icra.org>, Mark Nottingham <mnot@mnot.net>, www-tag@w3.org, Jonathan Rees <jar@creativecommons.org>

Jonathan, you may want to note the GRDDL WG's use-case [2].

Alan Ruttenberg wrote:

[snip]
> Isn't a "profile" just like any other document that defines a number
> of relationships? The current name for such things are "ontologies",
> and they generally live in RDF or OWL files. I guess I don't see why
> we need to introduce a new name here when we have a mechanism that
> works and is already part of the architecture. i.e. If a rel  is a URI
> that names a property, then we figure out what it means in the usual
> way - by doing a GET of the URI and looking at what is returned.
>
> In the case you give, I would write this as:
>
> Link-Prefix: "a", "http://profile.namespace.com/relation#"
> Link-Prefix: "", "http://www.iana.org/assignments/link-relations#"
> Link: <file.ext1>; rel="a:rel-1"
> Link: <file.ext2>; rel="a:rel-2"
> Link: <my.css>; rel="stylesheet"
>
> Assuming that "stylesheet" means the property
> <http://www.iana.org/assignments/link-relations#stylesheet>
> and that <profile.namespace> is actually some URI  such as
> "http://profile.namespace.com/relation#"
>
> To my mind this maximally borrows from current SW practice
>
> BTW, I don't have any preference for the syntax of the Link-Prefix
> header - could equally be any of
> Link-Prefix: "a";"http://profile.namespace.com/relation#"
> Link-Prefix: a=http://profile.namespace.com/relation#
> Link-Prefix: a;"http://profile.namespace.com/relation#"
I don't see how this gives us any advantage over just going with what is
in Mark Nottingham's latest draft [1], which is to just use rel=URI, as in:

Link: <file.ext1>; rel="http://profile.namespace.com/relation#rel-1"
Link: <file.ext2>; rel="http://profile.namespace.com/relation#rel-2"
Link: <my.css>; rel="stylesheet"

So "stylesheet" would resolve to
"http://www.iana.org/assignments/link-relations#stylesheet"

This solves the "profile" and "link" headers not matching up and
remaining ambiguous, is backwards compatible with non-URI link headers,
and solves our GRDDL use case [2] for using GRDDL. We'd have to do some
minor changes to our implementations and maybe a minor update to the
errata of spec and informative test-cases to make this work, but it
would work.

I think it wins because it does not introduce any new HTTP headers, and
so is parsimonious, while solving the problem. by relying on a very
minor change to Link's definition in HTTP. If it does not or creates new
problems, please explain.

[1]http://www.ietf.org/internet-drafts/draft-nottingham-http-link-header-01.txt
[2]http://www.w3.org/TR/grddl-scenarios/#header_use_case

    thanks,
          harry



> Best,
>
> -Alan
>
>>
>> Phil.
>>
>>
>>
>>
>> [1]
>> http://lists.w3.org/Archives/Public/ietf-http-wg/2008JanMar/0468.html
>>
>> Alan Ruttenberg wrote:
>>> Hi Mark,
>>> Having the link types be URIs will be a great help in solving a
>>> number of issues we've been dealing with around associating metadata
>>> with resources.
>>> I have one suggestion for the document - rather than having the
>>> link-extensions, with the default (i.e. not necessarily stated in
>>> the headers) base of
>>> http://www.iana.org/assignments/link-relations.html I would instead
>>> either leave that mechanism out, or add something like a
>>> Link-Prefix: header that allows one to set a prefix in the way one
>>> does for namespaces or RDF serializations.
>>> Ideally the IANA registry would be served as RDF (perhaps by
>>> conneg). In this way, resolution and discovery of relations could be
>>> uniform. An agent wishing to discover what
>>> Link-Prefix: "", "http://www.iana.org/assignments/link-relations#"
>>> Link: <http://www.cern.ch/TheBook/chapter2>; rel="Previous"
>>> Would do exactly the same thing as working with:
>>> Link-Prefix: "dc:", "http://purl.org/dc/terms/"
>>> Link: <http://mumble.net/~alanr/ThePersonAlanRuttenberg>;
>>> rel="dc:creator"
>>> Regards,
>>> Alan
>>> On Mar 19, 2008, at 3:11 AM, Mark Nottingham wrote:
>>>>
>>>> See referenced I-D for a rough idea of what I've been kicking
>>>> around WRT the Link header with a few people.
>>>>
>>>> Note that while it resolves the relation mess, it still has to get
>>>> some buy-in by both the HTML and Atom communities, as it asks some
>>>> non-trivial things of them.
>>>>
>>>> Also, this draft is still rough, with some outstanding issues
>>>> already identified. See discussion on the ietf-http-wg list.
>>>>
>>>> Cheers,
>>>>
>>>>
>>>> [ note: I've deleted the MIME attachment, because the last time I
>>>> forwarded this message, it appeared to crash Mail.app instances
>>>> that received it. Oops. ]
>>>>
>>>>
>>>>
>>>> Begin forwarded message:
>>>>
>>>>> From: Internet-Drafts@ietf.org
>>>>> Date: 18 March 2008 5:30:01 AM
>>>>> To: i-d-announce@ietf.org
>>>>> Subject: I-D ACTION:draft-nottingham-http-link-header-01.txt
>>>>> Reply-To: internet-drafts@ietf.org
>>>>>
>>>>> A New Internet-Draft is available from the on-line Internet-Drafts
>>>>> directories.
>>>>>
>>>>>
>>>>>     Title        : HTTP Header Linking
>>>>>     Author(s)    : M. Nottingham
>>>>>     Filename    : draft-nottingham-http-link-header-01.txt
>>>>>     Pages        : 13
>>>>>     Date        : 2008-3-17
>>>>>     This document clarifies the status of the Link HTTP header and
>>>>>  attempts to consolidate link relations in a single registry.
>>>>>
>>>>> A URL for this Internet-Draft is:
>>>>> http://www.ietf.org/internet-drafts/draft-nottingham-http-link-header-01.txt
>>>>>
>>>>>
>>>>> Internet-Drafts are also available by anonymous FTP at:
>>>>> ftp://ftp.ietf.org/internet-drafts/
>>>>>
>>>>> Below is the data which will enable a MIME compliant mail reader
>>>>> implementation to automatically retrieve the ASCII version of the
>>>>> Internet-Draft.
>>>>> ______________________
>>>>> I-D-Announce mailing list
>>>>> I-D-Announce@ietf.org
>>>>> https://www.ietf.org/mailman/listinfo/i-d-announce
>>>>> Internet-Draft directories: http://www.ietf.org/shadow.html
>>>>> or ftp://ftp.ietf.org/ietf/1shadow-sites.txt
>>>>
>>>>
>>>> --Mark Nottingham     http://www.mnot.net/
>>>>
>>>>
>>
>> --Phil Archer
>> Chief Technical Officer,
>> Family Online Safety Institute
>> w. http://www.fosi.org/people/philarcher/
>>
>>
>>
>
>


-- 
		-harry

Harry Halpin,  University of Edinburgh 
http://www.ibiblio.org/hhalpin 6B522426
Received on Thursday, 20 March 2008 20:37:20 GMT

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