Yadis 1.0

Yadis ID either is a http:/https: URL or resolves to a yURL (the Yadis URL)
Goal: ydocument (Yadis Document) or document at yrdURL (Yadis Resource Descriptor URL)

Not required to resolve non-URL things like XRIs.
URLs are retrieve via HTTP (with SSL if https:).

6.2.4. Initiation
(1)HEAD {yURL}
(2)GET {yURL}
(3)GET {yURL} && Accept: application/xrds+xml

6.2.5 Response
(1,2,3)-> X-XRDS-Location: {yrdURL}
(2,3) -> Content-Type: text/html [&& Vary:Accept] && <meta http-equiv="X-XRDS-Location" content="{yrdURL}" />
(3)-> Content-Type: application/xrds+xml && {ydocument}

-> Content-Type: text/html && <meta http-equiv="X-XRDS-Location" content="{yrdURL}" />
-> Content-Type: application/xrds+xml && {ydocument}
-> X-XRDS-Location: {yrdURL} && document(html=>ignore metas,application/xrds+xml(ignore))

HEAD {yURL}
-> X-XRDS-Location: {yrdURL}
   => GET {yrdURL}
-> anything else
   => GET {yURL}

GET {yURL} [&& Accept: application/xrds+xml]
-> X-XRDS-Location: {yrdURL}
-> Content-Type: text/html && <meta http-equiv="X-XRDS-Location" content="{yrdURL}" />
   => GET {yrdURL}
-> Content-Type: application/xrds+xml && {ydocument}
   => DONE
