Public Identifiers

John Cowan cowan at
Mon Sep 21 02:36:40 BST 1998

Steven R. Newcomb scripsit:

> Will URNs permit pointing to things that aren't now and may never be
> on the web? I mean, things that their owners never intended to be on
> the web and either that their owners do not want to appear on the web,
> or that their owners may not (currently) see any interest in putting
> on the web?

Clearly yes.  RFC 1737, "Functional Requirements for Uniform Resource Names",

# A URN identifies a resource or
# unit of information.  It may identify, for example, intellectual
# content, a particular presentation of intellectual content, or
# whatever a name assignment authority determines is a distinctly
# namable entity.  A URL identifies the location or a container for an
# instance of a resource identified by a URN.  The resource identified
# by a URN may reside in one or more locations at any given time, may
# move, or may not be available at all.

Note especially the last phrase.

> -//Sears, Roebuck & Co.//NONSGML TOPIC 1922 Farm Catalog Number : R205//EN

Does this refer to an actual gadget, the class of such gadgets, or
the description of it? The "EN" suggests that it refers to the
description only.

> Please let's not deprecate FPIs; instead,
> let's understand and celebrate the difference between FPIs and URNs,
> even if/when URNs are terrifically indirect.

RFC 1737 contemplates FPIs as a particular case of URNs:

# For example, ISBN numbers, ISO
# public identifiers, and UPC product codes seem to satisfy the
# functional requirements, and allow an embedding that satisfies
# the syntactic requirements described here.

A suitable URN representation of the above FPI would be:


encoded to remove illegal characters (namely spaces and slashes).
It's also necessary to encode "#", "?", and "%" when they appear in FPIs.
These rules are documented in RFC2141, "URN Syntax".

John Cowan					cowan at
		e'osai ko sarji la lojban.

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