1* ok, it's capital RECOMMENDED but I guess you can keep as you wish as long DE is working with it.
2* Found the shak! Okular is not accepting <opf:metadata> tags but only
<metadata> ones, as suggested in the specifications
(
http://www.openebook.org/2007/opf/OP...tml#Section2.2). I guess, again, you can drift from the specs as much as you wish
as long DE is working (I'll just write my python script to re-convert epub
into spec-compliant epub, nothing bad).
3* Ok, I was trying chapter recognition on Word created lits, where you have just the bold tag (<b>) available. I'll check XPath. Thank you.