Just require URLs

[Jeffrey E. Sussna]

There appear to be conflicts between RFC's 2396 (URI: Generic Syntax) and
2141 (URN Syntax). Interestingly, RFC 2396 is not specified as updating RFC
2141. In any case:

*Both specs agree that a URN must be preceded by the scheme "urn".

*RFC 2141 states that the forward-slash (and other reserved) character
should not be used in unescaped form, as its "applicability" is (or was at
time of writing, 5/97) still open to debate.

*RFC 2396, on the other hand, states that forward-slash (and other reserved)
character should not be used in unescaped form IF "the data...would conflict
with the reserved purpose". This seems to imply that it's ok to use "/"
unescaped if it denotes a hierarchical namespace.

*RFC 2396 APPEARS to state that an "authority" must be preceded by
double-forward-slash. It is not totally clear to me whether this applies to
the NID component of a URN.

First of all, I would be interested in opinions as to the above statements.
Secondly, I would be interested in opinions as to the advisability of going
ahead and using unencoded forward-slashes to denote hierarchy within a URN.
I need to denote such hierarchy, and it seems hard to believe that
forward-slash wouldn't be defined to denote such hierarchy. Thus encoding it
seems like a waste of time, effort, and an unnecessary loss of readability.

Jeff


> -----Original Message-----
> From: owner-xml-dev at ic.ac.uk
> [mailto:owner-xml-dev at ic.ac.uk]On Behalf Of
> Didier PH Martin
> Sent: Tuesday, June 01, 1999 12:12 PM
> To: 'XML Dev'
> Subject: RE: Just require URLs
>
>
> Hi Jonathan,
>
> Jonathan said:
>     Under the definition of URN in 2396, a URN is any URI
> whose intention is
> to reference an abstract resource, act primarily as a name,
> and/or not be
> retrievable via a network. Under the definition in 2396,
> "urn" defines a
> scheme/namespace (URI namespace) whose intention is to serve
> *only* for
> URNs, however the spec suggests that any scheme e.g. "http"
> can serve to
> define a URN, given the definition of URN in 2396 (part of
> which my earlier
> message quotes).
>
>     So, my reading of RFC 2396 and the XML namespace spec leads me to
> conclude that all URIs used as XML namespaces are properly
> URNs regardless
> of the URI scheme prefix.
>
> Didier says:
> This is not what RFC 2396 says. You are right when you say
> that a URI coudl
> be a URL or a URN. However a HTTP scheme cannot be considered as a URN
> because it is already part of the URL space.
>
> If however you create a name space having as NID "HTTP" then
> yes this would
> be a URN. However each "/" would have to be encoded. Thus, a
> URN cannot be
> with "/" as delimiters. Obviously we'll have to create a new RFC for
> hierarchical name spaces having "/" as delimiters but
> actually you would
> have to encode each "/". Thus your name space would look like:
>
> urn:http:domain.com%(hex for /)context%(hex for /)etc...
>
> The above URN confor to RFC 2141 specs. However the URL:
> http://domain.com/context/etc... do not conform to RFC 2141
> and thus cannot
> be said to be a URN.
>
> regards
> Didier PH Martin
> mailto:martind at netfolder.com
> http://www.netfolder.com
>
>
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