The Threshold Plug-in operates as a plug-in to the Alarm Application Services (AAS) and Alarm Mediation Services (AMS). It allows mapping rules to lookup numeric values present in alarm attributes in user defined ranges and receive a return value specific to the range in which the passed value is located. Ranges are defined in standard AAS/AMS XML datafiles. A typical example of usage would be where alarms contain cryptic variable numeric data which can be categorized into a range of thresholds equated to externally defined values that can add value to the alarm e.g. severity, location, priority classification etc.