The literature review on the production planning
of MTO systems reveals that the number of research
regarding the order entry stage is far less than the
job release and the dispatching stages. Hendry and
Kingsman (1989) first considered the order entry
stage in the production planning structure of MTO
systems. They emphasized that the key factor in
success of MTO systems is the order delivery time
management. Hence, before the job release and the
dispatching stages, it is necessary to launch the
capacity planning and control at the order entry
stage. In this regard, a hierarchical input–output
control was suggested across different stages of
production planning including the order entry stage.
The goal of input–output control proposed first by
Wight (1970) is synchronous control of inputs (i.e.,
customers’ demands) and outputs of the system (i.e.,
the capacity). Hendry and Kingsman (1993) also
suggested a method by means of an input–output
control approach in order to accept or reject the
new arriving orders. Since the delivery and manufacturing
lead times depend on the total backlog
(TB) and planned backlog (PB) (Plossl and Wight,
1973), they are controlled by means of defining
predetermined minimum and maximum values for
TB and PB. If the arrival of a new order causes TB
or PB to violate the predetermined values, either the
capacity is increased or the new order is rejected.
Easton and Moodie (1999) introduced a technique
that simultaneously optimizes pricing and lead time
decisions for MTO firms with contingent orders.
In recent years, the workload control approach
(WLC) has been considered by researchers to
investigate the order entry stage. This approach is
an extended input–output control approach, in
which the amount of input workload and the
capacity are controlled simultaneously. In this
regard, three relatively different approaches
have been introduced by Bertand and Wortmann