Dave Mcalpin has an article at Network World on XRIs. XRIs are useful for creating identities for abstract resources. That is, the XRI not only abstracts the location (URI) allowing multiple physical resources to represent a single abstract resource, but also gives other metadata that identifies and describes the abstract resource.

XRIs build on the ubiquitous Uniform Resource Identifier (URI) and Internationalized Resource Identifier (IRI) standards - widely used by identity management solutions - by defining standard ways to express characteristics such as type, language and date. The lightweight HTTP- and XML-based XRI resolution framework lets a consuming application quickly and easily discover metadata about those resources, such as an alternative synonym identifier that works better in the application's local identity management system.

Metadata isn't limited to alternative identifiers. Imagine that an XRI-identified resource is a technical manual, available as a PDF or Word document and retrievable from a variety of mirrored network locations via various protocols. In a broad sense, the manual is the same document irrespective of where it is located, how it is retrieved or in what format it is represented. XRIs are ideally suited for identifying resources at this level of abstraction because the resolution process lets the consuming application choose the best network location, retrieval method and file format for its needs from the available options.

Like URIs, XRIs are composed of an authority portion and a path portion. XRI resolution converts the authority portion and the path portion of an XRI to an XML document called an XRIDescriptor. The XRIDescriptor describes the identified resource and the means by which the digital representation of the resource can be retrieved. By providing an additional level of in direction away from concrete instances of a resource, XRIs provide a permanent, unbreakable reference on which stable business relationships can be based.

From XRIs resolve identity management dilemma
Referenced Thu Sep 22 2005 08:23:45 GMT-0600 (MDT)

We'll hear more about XRIs (and other solutions to problems in the Internet identity space) at next month's Internet Identity Workshop. I hope to see you there.