Arithmetic steps operate on actualisation counts from business steps, being the number of business items actualising a business step with a date of today or with a date in the past. Arithmetic steps take the actualisation count and - by means of an EQUALS step - output a TRUE or FALSE as an input to a business step, a decision step, a logic step or a summation step. A SUM step directly follows a business step, a SUM step or an INCREMENT step, with no intervening steps. A SUM step takes two input routes and sums their two counts. The summed count is emitted on the outbound route of the SUM step. The target of the outbound route of a SUM step is another arithmetic step. When both input routes into a SUM step have been completely parsed, the step outputs a parsed status of TRUE.