Discovery process on RP

It's process for Relaying Party that provide endpoint and service description. Information about endpoint services are stored in XRDS document.

Previous picture shows how to get XRDS document. This document contains information where is technical enpoint that understand OpenId protocol. Discovered XRDS document can contain multiple service sections. Each Service section describe one endpoint technical capabilities. Technical endpoint is tag URI. Multiple tags 'Type' specified technical options for given endpoint. Following diagrams shows how relaying party select proper endpoint for OpenID version 2.0.

1. Select OpenID 2.0 related services. This are services containing Claimed identifier element or OP identifier element.
2. Order selected services by following criteria:
   1. OP identifier element, it's Type 'http://specs.openid.net/auth/2.0/server'
   2. Claimed Identifier Element, it's Type 'http://specs.openid.net/auth/2.0/signon'
   3. By value of attribute 'priority', lower priority is more relevant, when priority is missing treat is as big number.
3. Select first service from list and it's requested OP technical endpoint.

Yadis discovery on OP

Following diagram shows how OP should provide YADIS discovery document.