1 "User" in terms of "customer".
2 The term "efficient" is used both in a functional and economic meaning throughout this chapter.
4 Since the approach presented in this paper also examines the functional and economic aspects of payment systems, the term 'security' is used in an equivalent way to functional and economic efficiency.
5 Mostly used in connection with the value benefit respectively scoring method.
6 Based on "n*(n-1)/2".