Meaning of osd xml-files



Hello, 
my question may seem strange, as I have been modifying the Titan skin for years.
But what exactly is the function of the following files?

Code:
DialogFullScreenInfo.xml
DialogSeekBar.xml
MusicOSD.xml
MusicVisualisation.xml
VideoFullScreen.xml
VideoOSD.xml

In the Titan skin, almost all of the functionality of these files is handled in a single file, the IncludesOSD.xml. The actually desired behavior is represented/reproduced with a bunch of visible conditions, which makes maintaining the skin quite complex.
(the DialogFullScreenInfo.xml file does not even exist under the Titan skin)

Is the DialogFullScreenInfo.xml for videos the same as the MusicVisualisation.xml for music?
What is the difference between VideoFullScreen.xml and DialogFullScreenInfo.xml?

(my actual goal is to move the functionality contained in the IncludesOSD.xml back into the original files, because the IncludesOSD.xml is a hell of ‘conditionals’, ‘visibles’ and ‘includes’…)