Predecessors

FAST does Predecessors!  In fact, FAST does entire precedence networks like those found in project scheduling, PERT, and CPM schedulers.  A precedence network is formed when an activity has several predecessors (activities that must be finished before it can start) and each of those predecessors has multiple predecessors and so on.  These networks are usually seen in projects like construction where there is a start time and then certain activities must be completed in order before the end of the project is reached.

The FAST system allows users to define activities, assign priorities and also specify as many predecessor activities as desired.  It even allows users to define a minimum separation time or maximum overlap time between activities.  Not only that, unlike most project schedulers, the FAST system allows users to define any number of time-varying resource requirements for each activity. (See previous postings on this.)

So here’s how FAST handles this amazingly general description.  When running as an automated scheduler, the FAST system finds the highest priority activity remaining and then chases its predecessor network backwards recursively so that all required predecessors are considered for scheduling before the selected activity. Of course all resources requirements are enforced as the system does this.  If a predecessor cannot schedule, the activity will not schedule and the system will provide the explanation for this.  That is, FAST will tell the user that the activity could not schedule because a predecessor was not scheduled.

The FAST system does all of this fast and finds solutions to situations involving both predecessors and resource constraints that other systems cannot find.  And the system supports easy unscheduling and rescheduling when limiting constraints have been encountered.

If you have been reading the previous postings, you can see the descriptive generality and solution capabilities of the FAST system are indeed unique.  Please read the next post to see how constraints can be relaxed, enforced, or tracked to facilitate capacity planning and “What-If” analyses.