Why does `xdg-mime query filetype ...` fail to find a new added file type?

I think I find the answer. On my system "xdg-mime query filetype ..." uses"file" command to get the file type, while on ubuntu it uses "gnomevfs".

It seems the "file" command does not check xml entries of shared-mime-info, but looks into the file "/user/share/file/magic" to get the file MIME type.

If I use "file" command on Ubuntu, it can not tell me the right MIME type, either.