1. A diagnoser performance measuring system for measuring performance of a diagnoser device of an aircraft system, said diagnoser device including: a first knowledge base having a first memory that includes data that comprises information related to a set of failures of the aircraft system, effects observed in real-time, during a flight, on the aircraft system caused by the set of failures, and relations between said set of failures and said effects observed; and an algorithmic core in the diagnoser device linked to the first knowledge base, the algorithmic core being configured to generate a diagnosis of the aircraft system; the diagnoser device being coupled to one or more sensors placed on the aircraft system and configured to transmit one or more messages to the diagnoser device, said messages carrying information about the effects observed on the aircraft system; the diagnoser performance measuring system comprising: a supplemental knowledge base having a second memory externally coupled to the diagnoser device, said supplemental knowledge base including, in addition to the data of the first knowledge base, a predetermined list of messages actually transmitted from the one or more sensors of the aircraft system to the diagnoser device, wherein the first knowledge base does not have the predetermined list of messages actually transmitted to the diagnoser device; a diagnoser performance evaluation computer device configured to carry out a performance evaluation of the diagnoser device and externally coupled to and separate from both the diagnoser device and the supplemental knowledge base, said diagnoser performance evaluation computer device configured to execute computer executable code for: calculating, at the diagnoser performance evaluation computer device, a first detection rate and a first location rate uniquely representative of a first quality metric of the first knowledge base only, said first detection rate and said first location rate being respectively referred to as an expected detection rate and an expected location rate, said calculating being based upon the supplemental knowledge base, calculating, at the diagnoser performance evaluation computer device, a second detection rate and a second location rate representative of a second quality metric that is indicative of a quality of the first knowledge base and a quality of the algorithmic core taken together, said second detection rate and said second location rate being respectively referred to as an obtained detection rate and an obtained location rate forming a diagnosis of the aircraft system, said calculating being carried out based upon the messages transmitted to the diagnoser device, said messages being generated from the predetermined list of messages stored in the supplemental knowledge base, calculating, at the diagnoser performance evaluation computer device, the performance of the diagnoser device as a function of all of the expected and obtained detection rates and of the expected and obtained location rates, and outputting the calculated performance from the diagnoser performance evaluation computer device to identify individual failures for which the algorithmic core of the diagnoser device has a poor efficiency due to an insufficient number of the one or more sensors or a placement of the one or more sensors based upon the calculated performance of the diagnoser device, and the first knowledge base being configured to be reimplemented with a knowledge base capture device when the calculated performance calculated by the diagnoser performance evaluation computer device is less than a desired performance.