Automated method for generating symptoms data for diagnostic systems

A method of generating symptom electronic data for use in a diagnostic system (210). The method includes: i) obtaining (302) Failure Modes and Effects Analysis (FMEA) data for a target system, the data including a plurality of observations, each said observation including a set of at least one measurement associated with a fault state or a nominal state of the target system; ii) selecting (304, 306) a first said observation associated with a nominal state; iii) selecting (304, 306) a second said observation associated with a fault state; iv) identifying (306) at least one measurement in the second observation that is/are not present in the first observation, and v) generating the symptom data based on the identified at least one measurement.