Constraint-based Optimization: Judo for the Supply Chain
(Supply Chain Alert, June 2003)
By Chris Beck and Gene Freuder,
Cork Constraint Computation Centre
Judo is a bit counter-intuitive. Judo means the "gentle way:"
when faced with an attacking opponent, the response is not to meet the
opponent head-on, applying force against force. Rather the response is to
give way or to be compliant. In this way, the opponents force may be
turned and used against him.
This same philosophy is at the heart of constraint-based techniques that
are increasingly applied to manage global supply chains. Instead of
viewing the constraints on decisions as an opponent to struggle against,
they are used to restrict and evaluate the impact of supply chain
Imagine a simple supply chain where factories can ship products directly
to customers. When a new order arrives, a choice must be made to allocate
the order to a particular factory. Many constraints bear on this
decision: Is the factory technically able to manufacture the order? Does
the factory have sufficient production capacity? Does the third-party
logistics company contracted for a factory have sufficient capacity to
make the delivery? What is the cost of production and delivery? These
constraints can be used to make the decision easier. Initially, we might
entertain the possibility of assigning the order to any factory and we
may be at a loss for deciding amongst them. By applying the constraints,
we can narrow the decision-making.
Obviously factories that are technically unable to manufacture the order
can be ignored for this decision. Next we can look at the available
capacity of the factories and logistics companies to reduce our options
to those that can feasibly produce and deliver by the required due date.
Finally, we can reason about the costs: of the feasible factories, which
can deliver with minimum production and delivery costs? The use of the
constraints limits the final options that must be investigated in depth.
Some constraints are "hard," e.g. the capacity of a shipping
container, while others are "soft," e.g. a preferred delivery
date. Researchers are even beginning to reason with
"stochastic" or uncertain constraints, like customer demand.
Many of the basic constraint-based techniques can be found within
existing supply chain management software from such companies as SAP and
Oracle. Research is focusing on some of the deeper issues that are not
yet addressed by commercial software. The Cork Constraint Computation
Centre (4C), a 9 million euro research center established by Science
Foundation Ireland, is at the forefront of this research. Using learning
and knowledge-based techniques, 4C is working to reduce the deep
technical knowledge required by people who implement constraint-based
supply chain solutions. Currently, highly skilled consultants are
required to implement supply chain optimization models. The goal of the
research is to provide an environment where experts in the supply chain
of a company can create, evaluate, and use constraint technology to aid
in decision making.
The need for a company to hire a black belt in optimization technology to
implement a supply chain solution may soon be a thing of the past.
Through the work of 4C and others, an internal company expert will be
able to make use of the distilled and automated experience of previous
supply chains to develop customized solutions: the "gentle way"
For more information about the work of the Cork Constraint
Computation Center, see
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