Re: The UR* scheme registry, Citing URL/URI specs

Dan Connolly (
Thu, 23 Oct 1997 23:30:25 -0500

Message-ID: <>
Date: Thu, 23 Oct 1997 23:30:25 -0500
From: Dan Connolly <>
To: Larry Masinter <>
Subject: Re: The UR* scheme registry, Citing URL/URI specs

Larry Masinter wrote:
> Dan,
> If you had control over this, which would you prefer? And why?

If it were just up to me, I'd choose URI (for the scheme
registry, process, and syntax drafts) because I
find the word 'identifier' more descriptive of the
concept of "string/symbol that refers to a resource."

The following explanation made sense when I first
read it, and still seems to make sense to me:

Name or Address, or Identifier?

Conventionally, a "name" has tended to mean a logical way of
referring to an object in some abstract name space, while the term
"address" has been used for something which specifies the physical
location. The term "unique identifier" generally referred to a name
which was guaranteed to be unique but had little significance as
regards the logical name or physical address. A name server was
used to convert names or unique identifiers into addresses.

With wide-area distributed systems, this distinction blurs. Locally,
things which at first look like physical addresses develop more and
more levels of translation, so that they cease to give the actual
location of the object. At the same time, a logical name or a unique
identifier must contain some information which allows the name server
to know where to start looking. In a global context, for example
"1237159242346244234232342342423468762342368" might well be
unique, but it contains insufficient (apparent) structure for a name
server to look it up. The name "" has a structure which
allows a search to be made in several stages. In fact, practical
systems using unique identifiers generally hide within them some
clues for the name server, such as a node name.

A hypertext link to a document ought to be specified using the most
logical name as opposed to a physical address. This is (almost) the
only way of getting over the problem of documents being physically
moved. As the naming scheme becomes more abstract, resolving the
name becomes less of a simple look-up and more of a search.

One expects in practice the translation of a document name taking
several stages as the name becomes less abstract and more
Tim BL 1991

Hmmm... the original WAIS documentation had some similar
stuff in an article about document identifiers,
but I can't find it anywhere on the web!