@ Kovid,
regarding idpf.org links. They start to be not reachable anymore. Here you will find some background information:
https://www.w3.org/2017/01/pressrele...nation.html.en
This should be the adequate link:
https://www.w3.org/Submission/ and
https://www.w3.org/Submission/2017/S...ages-20170125/