How to create values in XMP to allow you to search for similar images.
Where: Channel | Metadata | General tab
Color Factory can analyze images and create a similarity index that is stored as a 'checksum' in an XMP field. This allows FotoStation and FotoWeb to sort files by similarity. It should be noted that there is no face or shape recognition involved in this process; it is based on analyzing the color balance in the image and finding images with similar colors.