1. A method of evaluating differences between a first data set and a second data set for one or more computer systems comprising: obtaining said first data set and said second data set; selecting a parameter according to a differential rule definition; comparing said parameter in said first data set to said parameter in said second data set; determining if a difference in said parameter exists between said data sets; if said difference exists, applying a weight indicative of the relative importance of said difference in said parameter according to said differential rule definition; and providing an evaluation of said difference according to said weight.