1. A method for providing a function for use in detecting a presence of an exception in multidimensional data, comprising: partitioning said multidimensional data into at least a first region and a second region; assigning a first region-specific function to said first region and a second region-specific function to said second region; and determining a combined function from said first region-specific function and said second region-specific function, wherein said combined function is used to calculate an expected value of the multidimensional data for distinguishing the presence of an exception.