Re: URx Questions

On 2002-01-21 20:35, "ext Mark Baker" <> wrote:

> Patrick, I'm trying hard to understand your position here.  In as few
> words as possible, what's your definition of an URL?
> MB

Though I probably will need to provide a more lengthy explanation...

In a nutshell:

I view a URL as a direct point of access to a digital
resource, such that "interaction" with that point of access (whether
that be retrieval, storage, query, etc.) involves the interchange of
content between two systems -- a server which hosts that point of
access and a client which connects to that point of access.
Thus, a URL (e.g. 'http:') used to denote an abstract or non-digital
resource is not a "proper" or "reasonable" URL because it can never
meet the above expectations of accessibility.

A URN can be viewed as an indirect point of access to a digital
resource, such that -- as with a URL -- "interaction" with that
point of access involves the interchange of content. Thus, a URN
used to denote an abstract or non-digital resource is not a
proper or reasonable URN because it can never meet the expectations
of accessibility. In the case of a URN, the direct point of access
must be determined based on context or other external specification,
but otherwise, the interaction of a client with a URN denoted
resource is analogous to interaction with a URL denoted resource.

This does not mean that every URL or URN must always and forever
resolve in every context for all time to some digital
resource -- only that the original and intended purpose of every
minted URL and URN *is* to resolve to a digital resource.

In my I-D draft-pstickler-uri-taxonomy-00, I define a set of
primary distinctions between URI classes based on the denotation
of authorities/agencies in the URI scheme, such that, for a URL
both the minting authority and resolution (access) agency are
defined by the URL itself. For a URN, only the minting authority
is defined, leaving the resolution agency open to contextualization.

Without the distinction between directly resolvable (URL), indirectly
resolvable (URN), and non-resolvable (URP) inherent in the semantics
of each URI Scheme (and ideally, though not necessarily, organized
into a taxonomy of URI classes where significant intersection of
semantics occurs) applications are unnable to automatically
differentiate between a true access error and an "intentional"
access error -- the latter being the case in the use of URLs (or URNs)
for denotation of abstract and non-digital resources.

With regards to resolution, URLs and URNs are closely related, in
comparison to URPs -- as both URLs and URNs resolve to digital
resources (where URPs do not), and the primary difference between them
is simply whether access/resolution is direct or indirect based on
whether the resolution agency is specified in the URI itself.

With regards to named authorities/agencies, URNs and URTs are closely
related, with the primary difference between them being whether they
denote digital resources or non-digital resources (resolvable versus
non-resolvable) -- with both naming the minting authority but not any
resolution agency.

URVs are unique in that they name neither the minting authority nor
resolution agency (the latter of course because they are URPs and
non-resolvable) -- such that anyone can mint them so long as they
conform to the lexical requirements for the URV scheme, and they
become completely "free" and "unbounded" digital resources without
reference nor tie to creator or resolver. Any means to derive a source
for a given URV (e.g. analyzing a UUID, etc.) is an artifact of a
given URV scheme and not an inherent part of its interpretation.

Does that help clarify my understanding of URL, URN, etc.?



Patrick Stickler              Phone: +358 50 483 9453
Senior Research Scientist     Fax:   +358 7180 35409
Nokia Research Center         Email:

Received on Tuesday, 22 January 2002 02:20:11 UTC