. . "wishes to calculate the velocity for the specified field, represented by nS, nM, nH, nD or nW, where n is an integer and S, M, H, D or W specify seconds, minutes, hours, days or weeks. [0331] Once one or more velocity rules are defined, the rule engine 112 is restarted in order to register the new rules. [0332] The rule engine 112 API includes functions to effect the use of velocity rules by the f" . . .