Extensible Resource Identifier

Extensible Resource Identifier (abbreviated XRI) is a scheme and resolution protocol for abstract identifiers compatible with Uniform Resource Identifiers and Internationalized Resource Identifiers, developed by the XRI Technical Committee at OASIS. The goal of XRI is a standard syntax and discovery format for abstract, structured identifiers that are domain-, location-, application-, and transport-independent, so they can be shared across any number of domains, directories, and interaction protocols.

The XRI 2.0 specifications were rejected by OASIS, a failure attributed to the intervention of the W3C Technical Architecture Group which recommended against using XRIs or taking the XRI specifications forward. The core of the dispute is whether the widely interoperable HTTP URIs are capable of fulfilling the role of abstract, structured identifiers, as the TAG believes, but whose limitations the XRI Technical Committee was formed specifically to address.

The designers of XRI believed that, due to the growth of XML, Web services, and other ways of adapting the Web to automated, machine-to-machine communications, it was increasingly important to be able to identify a resource independent of any specific physical network path, location, or protocol in order to:

• Create structured identifiers with self-describing "tags" that can be understood across domains.
• Maintain a persistent link to the resource regardless of whether its network location changes.
• Delegate identifier management not just in the authority segment (the first segment following the "xxx://" scheme name) but anywhere in the identifier path.
• Map identifiers used to identify a resource in one domain to other synonyms used to identify the same resource in the same domain, or in other domains.

This work led, by early 2003, to the publication of a protocol based on HTTP(S) and simple XML documents called XRDS (Extensible Resource Descriptor Sequence).