1. A computer-implemented method of profiling a data set in a parallel processing environment, comprising: partitioning an initial data set vertically according to multiple attribute subsets; profiling one or more of the attribute subsets; generating a list of subjects or otherwise horizontal component values corresponding to a specific attribute value identified in the profiling; extracting values of multiple attributes for each said identified subject or otherwise horizontal component values; assembling sample results of said identified subjects or otherwise horizontal component values; merging the sample results to form a profiled subset of the initial data set; and transmitting, displaying or storing the profiled subset of the initial data set, a further processed version, or combinations thereof.