Before I started to use Okular, I was a user of Xournal, because I have been using Gnome and Ubuntu, and didn't know any application other than Xournal which can make pdf annotations. I created some annotations for a pdf file under Xournal, and saved the annotations to a .xoj file (which seems to be in xml format).

Later I managed to install Okular on my Ubuntu, which was troublesome, and started using Okular ever since, because I don't know any application comparable to or better than Okular for my use.

Now I would like to know if it is possible to load the annotations in the .xoj file when I open the pdf file in Okular, and if I can convert the annotations to a formal that Okular can recognize?

If Okular doesn't suport the Xournal annotation file yet, can I make a feature request?

Is it difficult to understand the annotation formats of Okular and of Xournal to make the convertion mannualy or by writng a program?
Any resources to get to know the annotation formats of both?

Thanks.