When no headers are present in the datasets to identify each variable or attribute, GeneXproTools assigns automatically an index to each variable, for instance, d0 corresponds to the variable in the first column, d1 to the variable in the second, and so on. When headers are used though, they can be used not only to generate more intelligible code by choosing Use Labels in the Model Panel, but they also make things more intelligible as they are used in the Variable Heat Maps of the Run Panel, in the Data Panel, and in the History Section of the Report Panel. Notwithstanding, in either case GeneXproTools uses internally the d0 – d(n-1) notation and in fact uses it in both the parse trees and the compact Karva code.