I just added XRDS (Extensible Resource Descriptor Sequence) as a new category on my blog because this simple XML document format, created by the OASIS XRI Technical Committee to provide XRI resolution metadata and subsequently adopted by Yadis, is starting to gain attention as the discovery format for OpenID.

Phil Windley just posted a good overview of XRDS today. For even more detail about XRDS (and OpenID in general) see this article written for the Java community — perhaps the single best technical article on OpenID I’ve read.