Let's do a small wrap up of the main concepts seen so far. Each directory under tags/ is a tag. If you copy a file under the tags/ directory it gets tagged. You can establish relations between tags using the relations/ directory. If tag A includes tag B all the files tagged as B will show up in tags/A/@/.
So far, so good. Now imagine that you tagged your mp3 library by band name and then organized the band tags by genre. In the end you included all the genre tags in music. Something like:
$ cp the_number_of_the_beast.mp3 ~/myfiles/tags/iron_maiden/@
[... other files too ...]
$ mkdir ~/myfiles/relations/heavy_metal/includes/iron_maiden/
[... other bands too ...]
$ mkdir ~/myfiles/relations/music/includes/heavy_metal/
[... other genres too ...]
$ ls ~/myfiles/tags/music/@
[... your whole library here ...]
Amazing! All your files in one place, without having to tag them as music one by one. You open your favorite music player, click on the_number_of_the_beast.mp3 and... the smooth timbre of a piano spreads in the room. What the hell happened to distorted guitars? Oh, sure, now you remember: that version is a tribute cover by a classical piano player. Better move it to ~/myfiles/tags/classical/piano/@:
$ mv ~/myfiles/tags/music/@/the_number_of_the_beast.mp3 ~/myfiles/tags/classical/piano/@
You give the move command and... the file is still there?!?!
Of course it is, because the reasoner knows that the music tag includes both classical and piano tags too, so your file still features in the result of tags/music/@. But how could you know the moving (retagging) happened? The reasoner prevents you from being sure.
The answer is: avoid the reasoner! If you end a query with the special @@/ marker, the reasoner doesn't get involved, so only files with an explicit match are returned. In example, if you list tags/music/@@/, then no files are listed, since music is by itself totally empty. The very same happens if you list tags/heavy_metal/@@/. But if you list tags/iron_maiden/@@/, all your Iron Maiden songs are there.
The @@/ marker is usually applied to single tag queries, like tags/iron_maiden/@@/ to ease the retagging process.
