Under Yadis is defined as a protocol and a data format with which information about supported services of an HTTP URL can be described and accessed in the concept of URL-based identity.


YADIS was the original working title of the OpenID concept by Brad Fitzpatrick. The title was, now in lowercase (because it should not be understood as an acronym of " Yet another distributed identity system" ), taken up again in the summer of 2005 and refers to an interoperability initiative between OpenID and LID. , The XRI - Team (i -names ) supported the concept and contributed XRDS as the data format in. Besides the founder company Six Apart, and NetMesh cordance currently support especially several small American businesses the initiative, but also the likes of VeriSign experimenting with Yadis and OpenID.

Yadis turned out subsequently to be as useful for URLs and XRIs out that the URL-based use of XRDS was formally added to the XRI Resolution 2.0 specification in November 2007.


A URL is the Yadis URL adduced by an XRDS document. This can be found in three different ways:

  • A special HTTP request, the header Accept: contains application / xml xrds
  • A X - XRDS location header in the HTTP response
  • Via a meta tag http -equiv = "X- XRDS - Location"

In the first case you have already received the XRDS document, in the last two cases, it must be requested with a second HTTP request.

Data format

The data format is based on XML and consists of service declarations ( services). Each service has an identified by a URI type and, if necessary, a URL under which the service is offered.

A typical XRDS document as it is delivered, for example, at LiveJournal looks like this:

                           Http://openid.net/signon/1.0 < / Type>              Http://www.livejournal.com/openid/server.bml < / URI >               Web Links

  • Identification technology
  • World Wide Web