1. A method of metering usage of software products on a data processing system, the method including the steps of: detecting an event indicative of the use of at least one product module on the data processing system; checking a catalogue containing a plurality of product identifiers to determine if the at least one product module has a corresponding product identifier; responsive to a determination that the at least one product module has no corresponding product identifier, determining a matching score indicative of a similarity of the at least one product module with each of the plurality of product identifiers; and responsive to a highest of said matching scores satisfying a threshold, adding an entry in the catalogue corresponding to said product module.