Tagxfs is a semantic file system. It extends the user space file system to a tag based hierarchy.
Imagine that you want to add a new folder to your existing folder structure. But semantically it belongs into more locations, e.g. you have the trailer for the movie 'Indiana Jones 4' and existing a folder structure (ref.1.1). It belongs in the folder Adventure and also in 2000s (production year 2008).
TMSU is a tool for tagging your files. It provides a simple command-line tool for applying tags and a virtual filesystem so that you can get a tag-based view of your files from within any other program.
TMSU does not alter your files in any way: they remain unchanged on disk, or on the network, wherever you put them. TMSU maintains its own database and you simply gain an additional view, which you can mount, based upon the tags you set up. The only commitment required is your time and there's absolutely no lock-in.