Yadis
Under Yadis refers to a protocol and a data format with which information about supported services an HTTP URL in the concept of URL-based identity can be written and retrieved.
background
YADIS was the original working title of Brad Fitzpatrick's OpenID concept . The title was now in lowercase (as it does not exceed acronym of " Y et a nother d istributed i Dentity s should be understood ystem"), taken up again in summer 2005 and called interoperability between OpenID and offensive LID . The XRI team ( i-names ) supported the concept and contributed XRDS as the data format. In addition to the founding companies SixApart , NetMesh and Cordance , several small American companies are currently supporting the initiative, but big names such as VeriSign are already experimenting with Yadis and OpenID.
Yadis then turned out to be so useful for URLs and XRIs that in November 2007 the URL-based use of XRDS was formally added to the XRI Resolution 2.0 specification.
protocol
A URL becomes a Yadis URL by presenting an XRDS document. This can be found in three different ways:
- Via a special HTTP request that contains the Accept: application / xrds + xml header .
- Via an X-XRDS-Location header in the HTTP response.
- Via a meta tag with http-equiv = "X-XRDS-Location".
In the first case you have already received the XRDS document, in the last two cases it has to be requested with a second HTTP query.
Data format
The data format is based on XML and consists of service declarations (services). Each service has a type identified by a URI and, if necessary, a URL under which the service is offered.
A typical XRDS document, such as that provided by Livejournal , looks like this:
<?xml version="1.0" encoding="UTF-8"?>
<xrds:XRDS xmlns:xrds="xri://$xrds" xmlns="xri://$xrd*($v*2.0)">
<XRD>
<Service>
<Type>http://openid.net/signon/1.0</Type>
<URI>http://www.livejournal.com/openid/server.bml</URI>
</Service>
</XRD>
</xrds:XRDS>