Comparison of signature file models with superimposed coding

The current study considers the superimposed coding variation of the signature file method (SC-SF). A number of issues which are not clearly specified in the literature are addressed by adopting a unified approach which makes possible the comparison of two SC-SF models. Heuristic analytic derivations of earlier studies are shown to be valid by analysis and calculation. The study identifies a clear advantage of one model over the other, in a way which is quite the opposite to what has been suggested in the past.