FW: Interpretation problems - perceived conflict between RFC 2141 and RFC 2396

Didier PH Martin martind at netfolder.com
Wed Jun 2 17:51:28 BST 1999


I posted your message in the URN WG mailing list and here is the answer from
one of the WG member.

Didier PH Martin
mailto:martind at netfolder.com
-----Original Message-----
From: Leslie Daigle [mailto:leslie at thinkingcat.com]
Sent: Wednesday, June 02, 1999 9:30 AM
To: martind at NETFOLDER.COM
Subject: Re: Interpretation problems - perceived conflict between RFC
2141 and RFC 2396


Thanks for forwarding the questions.

> *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
> character should not be used in unescaped form IF "the data...would
> with the reserved purpose". This seems to imply that it's ok to use "/"
> unescaped if it denotes a hierarchical namespace.

Actually, I read the words to the contrary.  I read these words to
say that unescaped "/" should be interpreted by the rules of hierarchy
laid out in 2396, and any other expected interpretation requires
the character to be escaped.

2396 defines a particular mechanism for interpreting and manipulating
hierarchical structures of URIs -- denoted by the use of the forward
slash.  This includes the ability to make relative references, etc,
that we were never able to reconcile with the notion of providing
fixed, persistent references (URNs).

Rather than try to effect changes to that interpretation of "/" in
URIs, or subject URNs to all existing URI rules for handling
that hierarchy, we decided to abstain from the use of the character.

Note that this does not mean namespaces cannot use "/" to denote
hierarchy -- if it is escaped, it can be used for hierarchy as
it is understood local to a particular namespace (i.e., browsers
and editors will not attempt to create or interpret relative URIs
of them).

> *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
> the NID component of a URN.

Again, this is "authority" as it is defined by the URI syntax, subject
to the particular interpretation as laid out in 2396.  There are
other URI schemes that do not have an authority component preceded
by "//".

> First of all, I would be interested in opinions as to the above

See above.

> Secondly, I would be interested in opinions as to the advisability of
> ahead and using unencoded forward-slashes to denote hierarchy within a



More seriously, look a little more closely at the problem, and I
think you'll see the distinction we're trying to draw.

> 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
> seems like a waste of time, effort, and an unnecessary loss of

a) don't forget that URNs are not primarily targetted at being
b) is the hierarchy you are looking for really all the bells &
   whistles of relative URIs as found in 2369, in which case you
   may not be after a URN afterall.  You may want the resolution
   mechanisms laid out in, for instance, the NAPTR RDS, but those
   are already described in generic terms as being applicable to
   all URIs, not just URNs.




"My cat has all the answers.  But she claims     Leslie Daigle
   she doesn't know the questions."              leslie at thinkingcat.com


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