To implement a pull-driven approach, selective control is
needed over which resources to draw for any given activity.
This selection is driven by information not solely about
resources in the queues immediately preceding the activity
under consideration, but also about work-in-progress and
resources downstream (successor queues and activities) in the
process. Resources will get priority over others in the same
queue if they are known to match up with resources forecast to
be or already available in queues further downstream in the
process. This way, those downstream resources will not unduly
await their match and be in process for any time longer than
needed, though their planned processing sequence may be
violated.