1. A computer-based method for classifying an observed composite action, wherein the observed composite action comprises a combination of simple actions, comprising the steps of: receiving image data representing the observed composite action; generating a feature vector from said image data; generating a plurality of baseline reference vectors by combining two or more representations of simple actions, wherein said representations of simple actions are stored in a computer storage device; preprocessing the feature vector to modify the feature vector towards a baseline reference vector to form a modified feature vector; and classifying the observed composite action by comparing each of the baseline reference vectors to the modified feature vector.