A method and apparatus are provided for correlating events in a system. Problems and other events can, e.g., be detected in a system that generates symptoms or observable events. A computer-accessible codebook is provided that includes a mapping between each of a plurality of groups of possible symptoms and one of a plurality of likely exceptional events (e.g., problems) in the system. The system is monitored and one or more known symptoms generated by the system are detected. A mismatch measure is determined between each of the plurality of groups of possible symptoms in the mapping and the one or more known symptoms using a computer, while disregarding symptoms in the groups of possible symptoms not determined to be known. One or more of the plurality of likely problems is selected corresponding to one of the plurality of groups having the smallest mismatch measure.