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RE: URNs, Namespaces and Registries

From: Schleiff, Marty <marty.schleiff@boeing.com>
Date: Fri, 11 Aug 2006 11:22:10 -0700
Message-ID: <2C1C6A07EEDCB14ABBACAC793BF8BE9E02E96966@XCH-NW-6V2.nw.nos.boeing.com>
To: <www-tag@w3.org>

Comments on section 2.6 (Uniform access to metadata) of URNs, Namespaces
and Registries [1].

Perhaps the XRI notion of metadata differs from the other myRIs. It
certainly differs from what I've read in "The use of Metadata in URIs"
[2].

It's probably important to understand that XRI is not a single type of
identifier; rather, it's more of a framework within which other kinds of
identifiers can be expressed. OIDs, IP address, distinguishedName, UUID,
HIT, identifiers that are case sensitive, identifiers that are case
insensitive, numeric identifiers, and others can all be expressed within
the XRI framework. Now let's move on to XRI's notion of metadata. 

XRI metadata consists of tags/indicators/data about the _identifier_
instead of data about the named resource. Identifier metadata informs
XRI-aware applications about characteristics of the identifier.
Following are examples of why identifier metadata might be usefull:

To inform the application about normalization and matching rules for an
identifier expressed in an XRI. Simple string matching would not
recognize that the following two DNs are equivalent:

     cn=smith\, joe,ou=Marketing;   O=Acme; c=us
     CN="Smith, Joe";   OU=marketing,o=acme, c=US

To inform the application of inherent features of an identifier such as
an embedded check digit or some crypto properties like the identifier is
a hash of the subject's public key. For the application to derive any
value from such features, the presence of such features mst be conveyed
to the application.

To inform the application of non-http resolution capabilities that might
be native to the identifier (e.g., DNS, or Open Group's notion of UUID
pair where one UUID represents the issuing authority that assigned the
other UUID to a subject). 

To inform an application of how to treat an identifier like "1.2.3.4" --
such an identifier in an XRI will let the application know if it can
ping the value as an IP address, or treat it like an OID, or treat it in
some other fashion.

I think the statement in URNsAndRegistries [1] that "Naming authorities
can impose such constraints on the http: URIs under their control"  also
covers XRI metadata requirements if we use a naming authority like
"http://xri.net" instead of the "xri:" scheme.

[1] http://www.w3.org/2001/tag/doc/URNsAndRegistries-50.xml 
[2] http://www.w3.org/2001/tag/doc/metaDataInURI-31

Marty.Schleiff
Received on Friday, 11 August 2006 18:22:31 GMT

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