One day lost on a "known bug and limitation", grrr !
http://developer.mozilla.org/en/docs/E4X says "E4X doesn't support parsing XML declaration (<?xml version=...?>)", why didn't I noticed it ??!
Ok, I'm not the only one to blame I think... Why the hell does javascript report the "xml is a reserved identifier" when you *forget* (is the XML still valid without this declaration ?) to remove this declaration and how does it want you to know where it came from !?
It remembered the lack of error reporting of RDF, but thanks to my last re-reading of the docs, I finally find the answer, hurrah !

So, today I can truly begin my development (I've spending the end of the last week reading documentation).
The first things I've to do is :

• list the features I'll have to implement (in progress, coming)
• test some of the different techniques I've find to do some of the more useful and necessary features

After trying for a long time using these shitty RDF templates, I've begun coding some test apps who can download a file and parse XML.