OS X: Everything you need to use Smart Folders | Computerworld
▻http://www.computerworld.com/article/2476275/mac-os-x/os-x--everything-you-need-to-use-smart-folders.html
Once you create a Smart Folder it will automatically update itself with any relevant new files you add. Since the release of Mavericks, many Mac users have used Tags; I prefer Smart Folders, as I don’t need to remember to Tag things while I work.
Add tags programmatically
▻http://stackoverflow.com/questions/19720376/how-can-i-add-os-x-tags-to-files-programmatically
and from the command-line
▻https://github.com/jdberry/tag