An autonomic method for modifying a decision tree algorithm operating on a multi-terminal telecommunications system, wherein the decision tree algorithm is configured to analyse diagnostic data for each terminal in the telecommunications system and an outcome of the analysis is a first action, being that a service associated with the terminal being analysed is automatically restarted, or a second action, being that the service associated with the terminal being analysed is manually restarted, the method comprising the steps of: a) receiving a set of diagnostic data for the multi-terminal telecommunications system; b) generating a first candidate modification for the decision tree algorithm using a machine learning process using a penalty parameter, the penalty parameter being a compromise between first and second performance criteria of the multi-terminal telecommunications system; c) generating a first set of predictions of first actions and second actions by applying the decision tree algorithm including the first candidate modification to the set of diagnostic data for the multi-terminal telecommunications system; d) determining a first value of a first performance criterion and a first value for a second performance criterion for the decision tree algorithm including the first candidate modification based on the first set of predictions; e) generating a new penalty parameter based on a first difference between the first value for the first performance criterion and a first target thereof, multiplied by a first weighting, and a second difference between the first value for the second performance criterion and a second target thereof, multiplied by a second weighting, using a first ratio of the first weighting to the second weighting; f) repeating steps b) to e) for a plurality of iterations, wherein, in each iteration, the machine learning process uses the penalty parameter generated in the previous iteration; g) applying the decision tree algorithm including the candidate modification generated using the final penalty parameter from the final iteration from step f) to the diagnostic data for the multi-terminal telecommunications system to determine whether the first or second action should be applied to each terminal in the multi-terminal telecommunications system; and h) if it has been determined that the second action should be applied to a terminal, apply the second action respectively to the terminal. a) receiving a set of diagnostic data for the multi-terminal telecommunications system; b) generating a first candidate modification for the decision tree algorithm using a machine learning process using a penalty parameter, the penalty parameter being a compromise between first and second performance criteria of the multi-terminal telecommunications system; c) generating a first set of predictions of first actions and second actions by applying the decision tree algorithm including the first candidate modification to the set of diagnostic data for the multi-terminal telecommunications system; d) determining a first value of a first performance criterion and a first value for a second performance criterion for the decision tree algorithm including the first candidate modification based on the first set of predictions; e) generating a new penalty parameter based on a first difference between the first value for the first performance criterion and a first target thereof, multiplied by a first weighting, and a second difference between the first value for the second performance criterion and a second target thereof, multiplied by a second weighting, using a first ratio of the first weighting to the second weighting; f) repeating steps b) to e) for a plurality of iterations, wherein, in each iteration, the machine learning process uses the penalty parameter generated in the previous iteration; g) applying the decision tree algorithm including the candidate modification generated using the final penalty parameter from the final iteration from step f) to the diagnostic data for the multi-terminal telecommunications system to determine whether the first or second action should be applied to each terminal in the multi-terminal telecommunications system; and h) if it has been determined that the second action should be applied to a terminal, apply the second action respectively to the terminal.