1. A method for separating at least one of a first plurality of objects and a second plurality of objects into at least two groups, each of the first plurality of objects being related to at least one of the second plurality of objects, the method being performed by a data processor, the method comprising: dividing the first plurality of objects into a first plurality of object subsets; and partitioning the second plurality of objects according to at least one of said first plurality of object subsets to form at least two groups of the second plurality of objects.