Type 'man xattr' in your OS X terminal; isn't it what you want? xattr -s author George file (It might need a -w, I'm not sure as I'm writing it with my iPad)

Type 'man xattr' in your OS X terminal; isn't it what you want? xattr -s author George file (It might need a -w, I'm not sure as I'm writing it with my iPad) I'm not sure it's searchable though. But unless I'm very mistaken, mdls (metadata list) Is searchable. It lists what's been saved by Spotlight and you can add to it.