Project Plan 365 uses an enhanced scheduling engine starting from Precedence Diagram Method. Precedence Diagram Method (PDM) is a method for scheduling projects based on project start date and tasks duration and predecessors. The PDM algorithm allows only auto-scheduled tasks and all tasks need to be on the same indent level. Summary tasks, manual tasks, or other constraints like calendars and tasks constraints are not allowed. This algorithm is used to calculate early start date, early finish date, late start date, late finish date, and slack.
We enhanced this method in order to be used on general projects, where we can have any type of tasks (auto tasks, manual tasks, placeholder tasks, split tasks, null tasks and summary tasks). Also, this new method allows having constraints and considers calendars and resources. Also, all the constraints for a task and all types of predecessors are taken into consideration. For this, we create multiple graphs of tasks which allow us to find the optimal way to schedule a project.