1. A computer implemented Minimum Description Length (MDL) based method for constructing a summary of an event sequence S, the method balancing between over-generalizing and over-fitting descriptions of the event sequence S, the method comprising: receiving an event sequence S identifying events of different event types occurring over a time interval; segmenting the event sequence S into segments (S 1 ,. .. , S k ), wherein k is an integer, wherein the segmenting partitions the time interval into contiguous, non-overlapping intervals, wherein the segmenting minimizing a total cost T L (S,M) in bits for describing the event sequence S, wherein the total cost T L (S,M) in bits consists of a number of bits used to identify segment boundaries segmenting the event sequence S into segments (S 1 ,. .. , S k ) and a total local cost L L (S i ,M i ) in bits for describing each segment, wherein the total local costs L L (S i ,M i ) in bits consists of a number of bits used to identify a local model M i and a number of bits used to describe the corresponding segment S i using the local model M i , and wherein each local model M i groups one or more events of one or more events types within the corresponding segment S i into one or more groups based on a frequency of occurrence of the events; and outputting a summary for the event sequence S, the summary indicating the segments (S 1 ,. .. , S k ) and the groups.