Re: This problem is solved very neatly already. Has nobody noticed...?
To expand on the above, BeOS did the above well because it was so integrated into the OS and all applications made use of it. Scott Hacker had a
great article on BeOS filetypes at www.byte.com a while back that explained how apps such as the web browser would automatically fill in certain attributes for the user (such as the source URL, date it was downloaded, mimetype etc), and that mp3 rippers would populate the song title, author, track length etc.
My understanding is that the issue of filesystem metadata has been discussed on the Linux kernel mailing list, and Linus and co are trying to work on a proper implementation.