Background

The XML format used by XRDS was originally developed in 2004 by the

OASIS In ecology, an oasis (; ) is a fertile area of a desert or semi-desert environment'ksar''with its surrounding feeding source, the palm grove, within a relational and circulatory nomadic system.” The location of oases has been of critical imp ...

XRI (

extensible resource identifier An 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 OA ...

Technical Committee
as the resolution format for XRIs. The acronym XRDS was coined during subsequent discussions between XRI TC members and

OpenID OpenID is an open standard and decentralized authentication protocol promoted by the non-profit OpenID Foundation. It allows users to be authenticated by co-operating sites (known as relying parties, or RP) using a third-party identity provider ...

developers at firs
Internet Identity Workshop
held in Berkeley, CA in October 2005. The protocol for discovering an XRDS document from a

URL A Uniform Resource Locator (URL), colloquially termed as a web address, is a reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifie ...

was formalized as the

Yadis {{Unreferenced , date= November 2013 Yadis is a communications protocol for discovery of services such as OpenID, OAuth, and XDI connected to a Yadis ID. While intended to discover digital identity services, Yadis is not restricted to those. Othe ...

specification published b
Yadis.org
in March 2006. Yadis became the service discovery format for

1.1. A common discovery service for both URLs and XRIs proved so useful that in November 2007 th
XRI Resolution 2.0
specification formally added the URL-based method of XRDS discovery (Section 6). This format and discovery protocol subsequently became part o

XRDS Simple

In early 2008, work on

OAuth OAuth (short for "Open Authorization") is an open standard for access delegation, commonly used as a way for internet users to grant websites or applications access to their information on other websites but without giving them the passwords. T ...

discovery by Eran Hammer-Lahav led to the development of XRDS Simple, a profile of XRDS that restricts it to the most basic elements and introduces some extensions to support

discovery and other protocols that use specific

HTTP The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, ...

methods. In late 2008, XRDS Simple has been cancelled and merged back into the main XRDS specification resulting in the upcoming XRD 1.0 format.

Example uses

Besides

XRI An 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 OA ...

resolution, examples of typical XRDS usage include: *

authentication for discovery and capabilities description of OpenID providers. *

discovery for locating OAuth service endpoints and capabilities. * The Higgins Project for discovery of Higgins context providers.
XDI.org

I-name I-names are one form of an XRI — an OASIS open standard for digital identifiers designed for sharing resources and data across domains and applications.I-number i-numbers are a type of Internet identifier designed to solve the problem of how any web resource can have a persistent identity that never changes even when the web resource moves or changes its human-friendly name. For example, if a web page h ...

digital identity addressing services for generalized digital identity service discovery. * The

XDI XDI (short for "eXtensible Data Interchange") is a semantic data interchange format and protocol under development by the OASIS (organization), OASIS]XDI Technical Committee The name comes from the addressable graph model XDI uses: every node in the ...

data sharing protocol for discovery of XDI service endpoints and capabilities.

Example XRDS document

Following is an example of an XRDS document for the fictional

i-name I-names are one form of an XRI — an OASIS open standard for digital identifiers designed for sharing resources and data across domains and applications.HTTP The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, ...

HTTPS Hypertext Transfer Protocol Secure (HTTPS) is an extension of the Hypertext Transfer Protocol (HTTP). It is used for secure communication over a computer network, and is widely used on the Internet. In HTTPS, the communication protocol is enc ...

using the content type application/xrds+xml. Note that the outer container element serves as a container for one or more (Extensible Resource Descriptor) elements. Most simple XRDS documents have only one XRD. Other services like

resolution may construct a sequence of XRDs within a single XRDS document to reflect a chain of metadata about linked resources. *example 2008-05-05T00:15:00.000Z xri://= !4C72.6C81.D78F.90B2 http://example.com/example-user http://example.net/blog xri://=!4C72.6C81.D78F.90B2 xri://=!F83.62B1.44F.2813 xri://$res*auth*($v*2.0) application/xrds+xml http://resolve.example.com http://resolve2.example.com https://resolve.example.com http://specs.openid.net/auth/2.0/signon http://www.myopenid.com/server http://example.myopenid.com/ http://openid.net/server/1.0 http://www.livejournal.com/openid/server.bml http://www.livejournal.com/users/example/ /media/pictures image/jpeg http://pictures.example.com

Synonyms

XRDS documents can assert zero or more

synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

s for a resource. In this context, a synonym is another identifier (a

URI Uri may refer to: Places * Canton of Uri, a canton in Switzerland * Úri, a village and commune in Hungary * Uri, Iran, a village in East Azerbaijan Province * Uri, Jammu and Kashmir, a town in India * Uri (island), an island off Malakula Islan ...

) that identifies the same target resource. For instance, the example XRDS document above asserts four synonyms: # The local synonym !4C72.6C81.D78F.90B2. This is a relative

synonym assigned by the provider of this XRDS document. # The equivalent

http://example.com/example-user with a priority of 10 (1 is the highest priority). # The equivalent

http://example.net/blog with a priority of 15 (a lower priority than the other equivalent URL above). # The canonical identifier xri://=!4C72.6C81.D78F.90B2. This is an absolute

i-number i-numbers are a type of Internet identifier designed to solve the problem of how any web resource can have a persistent identity that never changes even when the web resource moves or changes its human-friendly name. For example, if a web page h ...

for the target resource—a persistent identifier that will never be reassigned (the functional equivalent of a

Uniform Resource Name A Uniform Resource Name (URN) is a Uniform Resource Identifier (URI) that uses the scheme. URNs are globally unique persistent identifiers assigned within defined namespaces so they will be available for a long period of time, even after the res ...

). For full details of XRDS synonym support, se
XRI Resolution 2.0
Section 5.

Service endpoints (SEPs)

The other main purpose of XRDS documents is to assert the services associated with a resource, called ''service endpoints'' or ''SEPs''. For instance, the example XRDS document above asserts four service endpoints for the represented resource: # An

resolution service (type xri://$res*auth*($v*2.0)). # An

2.0 authentication service (type http://openid.net/signon/2.0). # An

1.0 authentication service (type http://openid.net/server/1.0). # An untyped service for requesting resources with a

media type A media type (also known as a MIME type) is a two-part identifier for file formats and format contents transmitted on the Internet. The Internet Assigned Numbers Authority (IANA) is the official authority for the standardization and publication o ...

image/jpeg. For full details of XRDS service endpoints, se
XRI Resolution 2.0
Sections 4.2 and 13.

Service types

In XRDS documents, a service is identified using a

. Following are listings of well-known service types. See als
XRDS Type
a

begun in May 2008 to provide a catalog of XRDS service types.

XRI resolution

OpenID

OAuth discovery

Licensing

XRDS is an open public royalty-free

specification. Th
OASIS XRI Technical Committee
has operated since its inception in 2003 under a royalty-free licensing policy as stated in it
charter
an
IPR page

References

External links

OASIS XRI Technical Committee
*

– XRDS document format is specified in Section 4. *
OASIS XRI 2.0 FAQ

XRDS Simple 1.0

XRDS Type
– an open community registry of XRDS service types.
dev.xri.net
– an open public wiki on XRI and XRDS open source projects
Internet Identity Workshop One-Pager on XRI and XRDS
{{OASIS Standards XML-based standards