Graduation of the WBS cube’s axis, which concerns the ABS, PBS and ZBS axis of the 3D Gantt, is fundamental for the project interfaces calculation. This graduation allows to calculate the distance between two 3D little cubes (tasks) with the norm of vector formula, so the criticity of the interface can be calculated.
To graduate the axis, a scheduling must be launched, then the dates are calculated and it is then possible to calculate the barycentre, in terms of date, of each group of tasks that belongs to one Activity, Product or Zone. The coordinate of each Task is given by its mean date, the duration of the task is the weight for the barycentre calculation. The codification of the tasks allows to define which task belongs to which Activity, Product or Zone. The scheduling allows also to define if the task are running at the same, in others words if the tasks are really in interfaces. That’s why we say that the tree structures ABS, PBS and ZBS have a chronology, Activities, Products and Zones have a position in the time and on the WBS cube’s axis.
In the example below, the Product (PBS) axis is graduated, as explained before, with the help of the schedule.