Subject: Re: [urn] [apps-discuss] URNs are not URIs (another look at RFC 3986)

From: [email-masked] (Henry S. Thompson)
Date: Thu, 05 Jun 2014 13:48:04 +0100

I wrote:

> Let's take the e-book example (I'm using a DOI, because
> I happen to remember where to find the resolver for them, but the
> point would be the same for any URN->http:URI resolver today):  The
> following _both_ identify the main body of an editorial in the journal
> _Nature_ of 28 May 2014:
>
>  doi:10.1038/509534a#article
>  http://dx.doi.org/10.1038/509534a#article

So I was wrong to use the key term of art 'identify' above.  Somewhat
to my surprise, it turns out that in _neither_ case do we know what
the URI identifies, for different but related reasons in the two
cases.

Wrt the first case, as far as I can tell there _are_ no resolvers
available other than ones which translate at source into the second
case.

Furthermore, I can't find anywhere in DOI documentation any discussion
of an intended semantics for fragments.

Wrt this, and the second case, 3986 tells us that the ('secondary')
resource identified by a URI including a hash is

  "defined by the set of representations that might result from a
   retrieval action on the primary resource.  The fragment's format
   and resolution is therefore dependent on the media type [RFC2046]
   of a potentially retrieved representation, even though such a
   retrieval is only performed if the URI is dereferenced."
    http://tools.ietf.org/html/rfc3986#section-3.5

All attempts at retrieval wrt "http://dx.doi.org/10.1038/509534a",
however, result in a 303 response code, which means, _inter alia_,
that the representation retrievable from the supplied redirection is
_not_ a representation of the primary resource.

The relevance of this to the original question ("Does 3986
unacceptably constrain URN use?") remains to be explained.

I think, at least wrt fragments, the answer is "no", but I'll hold off
on trying to explain that until I hear more about what the
_requirements_ on fragments are that are behind the stated belief in
the current discussion that the answer is "yes".

ht

-- 
       Henry S. Thompson, School of Informatics, University of Edinburgh
      10 Crichton Street, Edinburgh EH8 9AB, SCOTLAND -- (44) 131 650-4440
                Fax: (44) 131 650-4587, e-mail: [email-masked]
                       URL: http://www.ltg.ed.ac.uk/~ht/
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