Just require URLs

Jeffrey E. Sussna jes at kuantech.com
Wed Jun 2 01:24:35 BST 1999

Thanks, your comments are very well put and helpful. I do not in fact intend
to use relative urn's. I do, however, need them to be as
human-readable/writable as possible, and hierarchy supports those
requirements in my case.


> -----Original Message-----
> From: Ron Daniel [mailto:RDaniel at DATAFUSION.net]
> Sent: Tuesday, June 01, 1999 3:33 PM
> To: 'Jeffrey E. Sussna'; 'XML Dev'
> Subject: RE: Just require URLs
> A pedantic point to clarify some of the confusion over '/' in URNs
> and URLs.
> RFC 2141 (the URN syntax spec) says that forward
> slashes SHOULD NOT be used in their unescaped form. The
> pedantic point is that to really really really forbid this,
> the spec would have said MUST NOT. (And I know for a fact
> that the choice of SHOULD NOT vs. MUST NOT was deliberate
> in this case).
> The use of '/' gets bound up with the question of 'relative
> URNs' and whether they are meaningful. The working group
> did not reach consensus on that point, so the compromise
> was to discourage the use of '/' but not totally forbid it.
> RFC 2396 is correct here. You MUST use '/' to denote hierarchy.
> If you want to use them for something else you MUST %encode them.
> If you want to do URNs with hierarchical levels in them, you
> MAY use '/' but you SHOULD NOT. (The reason for that, as I
> recall, is that it is very easy to break relative URNs.)
> Speaking personally, if I were sure that I would not be doing
> relative identifiers, I wouldn't let the "SHOULD NOT" stop
> me from using '/'.
> regards,
> Ron Daniel Jr.

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