It is common in XPAC project for the Zero Test Data Field for an activity to be the same as the Accumulation Field for a resource scheduling that activity. However, they do not have to be the same. The following example illustrates how the Zero Test Data Field and the Accumulation Field can be used to generate simple broadbrush schedules that are quite powerful in the results they generate.

Consider a deposit in which each Main database record can contain both Ore and Waste, but may only contain one of these. Ore and Waste are set up as two separate activities. Initially you want to run some broadbrush schedules on this deposit, to establish how the waste presents in relation to the Ore. To keep the schedules simple, only the Ore Tonnage will be scheduled.

For this example, the Zero Test Data Fields could be set up as follows.

Now assume that there is only one resource called Ore Miner and that it will target Ore Tonnes per Period. The aim of the schedule is to establish how much Waste Tonnage must also be mined in order to achieve the target Ore Tonnage. The accumulation field for this resource would be a Main database data field containing the ore tonnage.

Consider three records in the deposit as follows:

The Initial Mine Status for the Ore Mining activity has been set to 100% for each record since the zero test data field, Total Ore Tonnage, is greater than zero for all three records.

When the Ore Miner schedules the records above, the Output Path will appear as follows. Note that the order in which the records are scheduled does not matter in this example.

The key point in the schedule results presented in the table above is that for Block Z, the Ore Miner scheduled 100% of Zero Ore Tonnes. This may initially seem illogical, until it is looked at in a different light.

The schedule was instructed that any block which contained a Total Tonnage greater than zero should be available for scheduling (via the zero test data field). However, the rate at which the records were scheduled was controlled by the ore tonnage in each record (that is, the accumulation field and target for the resource). The aim of the schedule has been achieved, in that it has shown how much Waste Tonnage must be mined in order to achieve the target Ore Tonnage.

In a schedule such as this, the actual duration that is reported for each step in the schedule is not meaningful. However, as long as you are confident that the target Ore Tonnage can be achieved, this does not matter. If the Waste Tonnage reported to be mined is too great, then this indicates that the schedule is not achievable and that the schedule constraints must be changed (for example, the target Ore Tonnage, the mining sequence, etc).