!!! Overview [1]
[{$pagename}] ([Yet Another Distributed Identity System]) is a [Discovery Mechanism] of services such as [OpenID] (not [OpenID Connect]), [OAuth] (not [OAuth 2.0]), and [XDI] connected to a [Yadis ID]. 

While intended to discover digital identity services, [{$pagename}] is not restricted to those. Other services can easily be included.

A [Yadis ID] can either be a traditional [URL] or a newer [XRI] [i-name], where the [i-name] must resolve to a [URL]. The so-called [{$pagename}] [URL] either equals the [Yadis ID] (if this is a [URL]) or the resolved [URL] of the [XRI] i-name.

Furthermore, [{$pagename}] specifies how to use the [{$pagename}] [URL] to retrieve a service descriptor called Yadis Resource Descriptor. This descriptor follows the [XRDS] format and connects several services, like [authentication] or [authorization] to the Yadis [URL]. Each service description can have further parameters.

[{$pagename}] is really a [discovery|Discovery Mechanism] [protocol] was spearheaded by Brad Fitzpatrick, David Recordon (then both at Six Apart) and Johannes Ernst and Joaquin Miller (then both at NetMesh), in order to create an extensible foundation for [user-centric], decentralized, [web] [identity|Digital Identity].[2]

Over a period of several months, with the involvement of several dozen other individuals, the [{$pagename}] 1.0 specification was created and widely implemented on the web. 

The [{$pagename}] specification provides:
* A general purpose identifier for persons and any other entities, which can be used in a variety of services.
* A syntax for a resource description document identifying services available using that identifier and an interpretation of the elements of that document.
* A [protocol] for obtaining that resource description document, given that identifier.
Together these enable coexistence and interoperation of a rich variety of services using a single identifier. The identifier uses a standard syntax and a well-established namespace; it requires no additional namespace administration infrastructure. When a User offers a [Yadis ID] to a [Relying Party], that [Relying Party] will want to discover which services are available using that [Yadis ID].

!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]
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* [#1] - [Yadis|Wikipedia:Yadis|target='_blank'] - based on information obtained 2017-07-16- 
* [#2] - [Yadis|http://infogrid.org/trac/wiki/Yadis|target='_blank'] - based on information obtained 2017-07-16-