Project control aims at adhering to the resulting schedule. It
is assumed that all resources required to perform an activity that
is about to start will indeed be available at that activity's earlystart
time. In this so-called "push-driven" approach, each
activity passively waits for its ingredients (instructions, labor,
materials, equipment, and space) to become available, e.g., by
being released upon completion of predecessor activities. When
some have become available but others needed at the same time
have not, those available will wait in a queue or buffer for the
combination of resources— the set of "matching parts"— in its
entirety to be ready. While it may be possible to start work with
an incomplete set of resources, chances are this will negatively
affect productivity (e.g., Thomas et al. 1989, Howell et al.
1993).