I'm sure many moons ago in Aperture 2 when I trialled Silver Efex Pro that it automatically added a keyword “SFX-Pro” to the image I'd edited. I would really like to have this capability as I use the Nik suite quite a bit as well as CS5 & Perfect Resize 7. Sometimes I cannot remember if I've used Nik Sharpener for example.
I'm sure I never dreamt the auto-keywording. Did it exist? Maybe it was something NIK did? Is there a way to do this within Aperture?