From rankings' collinearity to counting SDR's via chromatic list expression.

The problem of counting rankings satisfying the collinearity condition with respect to two rankings over the metric spaces of rank distance is treated in this paper by transforming it into finding the number of systems of distinct representatives (abbreviated as SDR's) with respect to associated set systems. A formula for the chromatic list expression of graphs is then given in terms of the inclusion and exclusion principle, followed by a formula for the number of SDR's of set systems when the graphs are complete. [ABSTRACT FROM AUTHOR]