A computer system comprising one or more processors and computer-readable media operatively connected thereto, having stored thereon instructions for carrying out the steps of: maintaining one or more databases comprising first electronic data comprising digitally created reference compact electronic representations for each of a plurality of reference electronic works and second electronic data associated with the reference electronic works and related to action information corresponding thereto; obtaining a first digitally created compact electronic representation comprising one or more extracted feature vectors of a first electronic work; identifying a matching reference electronic work by comparing the first digitally created compact electronic representation of the first electronic work with the first electronic data using a sub-linear search of the first electronic data; determining the action information corresponding to the matching reference electronic work based on the second electronic data; and associating the determined action information with the first electronic work.