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RE: URNs?

From: Hires, Will E. <Will.Hires@jhuapl.edu>
Date: Mon, 22 May 2000 14:11:13 -0400
Message-ID: <19C5E1BF19A1D311ADAE0008C7918C4C47DBE5@aples4.jhuapl.edu>
To: www-amaya@w3.org
This list may have already had it's fill of information about URNs, but I
thought, despite this possibility, I would share the following:

In order to access information, one must be able to
discover or identify the particular information desired, determined
both how and where it might be used or accessed. The partitioning of
the functionality in this architecture is into uniform resource names
(URN), uniform resource characteristics (URC), and uniform resource
locators (URL). 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 uniquely 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.
Of course, not all resources will move during their lifetimes, and not
all resources, although identifiable and identified by a URN will be
instantiated at any given time. As such a URL is identifying a place
where a resouresce may reside, or a container, as distinct from the
resource itself identified by the URN. A URC is a set of meta-level
information about a resource. Examples of such meta-information are:
owner, encoding, access restrictions (perhaps for particular
instances), and location.

With this in mind, we can make the following statement:

The purpose or function of a URN is to provide a globally unique,
persistent identifier used both for recognition and often for
access to characteristics of or access to the resource.

More specifically, there are two kinds of requirements on URNs:
requirements on the functional capabilities of URNs, and requirements on
the way URNs are encoded in data streams and written communications.

These are the requirements for URN's functional capabilities:

* Global scope: A URN is a name with global scope which does not imply
a location. It has the same meaning everywhere.

* Global uniqueness: The same URN will never be assigned to two
different resources.

* Persistence: It is intended that the lifetime of a URN be permanent.
That is, the URN will be globally unique forever, and may well be used
as a reference to a resource well beyond the lifetime of the resource
it identifies or of any naming authority involved in the assignment of
its name.

* Scalability: URNs can be assigned to any resource that might
conceivably be available on the network, for hundreds of years.

* Grandfathering: The scheme must permit the grandfathering of existing
systems. For example, ISBN numbers, ISO public identifiers, UPC
product codes and the like are naming schemes which should be allowed
to be embedded within the URN system.

* Extensibility: Any scheme for URNs must permit future extensions to
the scheme.

* Independence: It is solely the responsibility of a name issuing
authority to determine the conditions under which it will issue a
name.

* Resolution: A URN will not impede resolution (translation into a URL,
q.v.). To be more specific, for URNs that have corresponding URLs,
there must be some feasible mechanism to translate a URN to a URL.
Received on Monday, 22 May 2000 14:11:20 UTC

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