Extensible Resource Identifier

XRI stands for Extensible Resource Identifier, an open standard protocol for digital addressing developed by the Organization for the Advancement of Structured Information Standards (OASIS), a non-profit consortium engaged in developing interoperability protocols for security, Cloud Computing, SOA, web services, the Smart Grid, electronic publishing, emergency management, etc.

XRI Resolution is defined as a simple and easy-to-deploy infrastructure for the purpose of resolving XRIs to Uniform Resource Identifiers (URIs). It uses the HTTPs, XRDS documents, and SAML assertions enabling the discovery and selection of service endpoint metadata for any type of service associated with a resource. XRI is able to meet the functionality requirements of the URNs (Uniform Resource Names), which is capable of identifying resources both people and organizations as well as sharing data across applications, domains and enterprises.

The XRI syntax was developed based on RFC 3986 on URIs, which provided a simple and extensible way for identifying a resource, and RFC 3987 on IRIs (Internationalized Resource Identifiers), a protocol with a sequence of characters from the Unicode/ISO 10646. XRI is capable of including characters beyond those used by the generic URI and incorporates the simplification and enhancements of the URI syntax. The OASIS XRI Technical Committee explained that just like the generic URI, the XRI syntax has four optional components with the scheme name xri: For example: xri: authority / path  ? query # fragment. The HTTP URIs, which use the generic URI syntax, can be changed to a valid XRI by simply changing an http URI to XRI just like this, xri://www.example.com/pages/index.html (standard HTTP URI converted to XRI).

Key Features XRI Provides

• Structured Identifiers
• Robust Synonym Expression and Resolution
• Uniform Extensible Discovery, Resolution, and Description Protocol

XRI Technical Committee

The XRI Technical Committee (XRI TC) was created for the purpose of defining the XRI. Drummond Reed from Cordance and Gabriel Wachob from VISA served as co-chairmen of the technical committee, leading the development of the following:

• XRI Primer v1.0 - Introduction to XRI and its uses
• XRI Metadata Specification v1.0 - A registry of special XRI identifiers which describes other XRI identifiers
• XRI Secure Resolution Specification v1.0 - Extensions to the base XRI resolution protocol for digitally verifying resolution results
• XRI Syntax and Resolution Specification v1.1 - A revision incorporating implementation experience and feedback

XRI Open Source Projects

There are different XRI open resource projects maintained by the XRI community, which include:

• OpenXRI
• Barx
• JanRain
• DotNetOpenId
• FoXRI
• AuthSrv
• PyAuthSrv
• Linksafe

Internet Community Reaction on XRI

The introduction of XRI stirred discussion within the Internet community. Tim Berners-Lee and Stuart Williams, co-chairs of the W3C Technical Architecture Group, expressed their dissatisfaction with the XRI Technology. Berners-Lee and Williams explained that they reviewed XRI and found that is has functionality that is not readily available from HTTP: URIs. According to them the XRI specification should not be supported. Some members of the Internet community expressed that the technology is untested and the registration process is confusing. Others advised consumers to avoid the service and commented that the Internet community did not need another centralized body to manage Internet addressing services.

Request For Comments

International Standards Organization

Hypertext Transfer Protocol