The Internet Encyclopedia (Volume 3)

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394 SUPPLYCHAINMANAGEMENTTECHNOLOGIES

to alternatives previously visited (considered “tabu”). It

also allows the search to cross boundaries of feasibility

by systematically imposing or releasing constraints to ex-

plore solutions that may reside outside local optimality. It

has proven to be useful in several areas of resource plan-

ning and design for SCM. More information can be ob-

tained on this topic from the bookTabu Search(Glover &

Laguna, 1997).

Simulated Annealing

This technique for optimizing solutions is based on a

theory from statistical mechanics. It works by simulat-

ing the process nature performs in optimizing the en-

ergy of a crystalline solid, when it is annealed to remove

defects in its atomic arrangement. It is used to approx-

imate the solution of very large optimization problems

and works well with nonlinear objectives and arbitrary

constraints. One criticism, however, is that it can be slow

in determining an optimal solution. More information on

this technique can be found inSimulated Annealing and

Boltzmann Machines: A Stochastic Approach to Combina-

torial Optimization and Neural Computing(Aarts & Korst,

1989).

Exhaustive Enumeration

This process involves looking at all possible alternatives

to find the best solution and is therefore only used when

there are few variable alternatives to evaluate. It takes

an enormous amount of computing power to evaluate all

possible combinations of a complex problem. Most SCM

problems are too large for this approach. Even with to-

day’s super computers, they cannot be completely enu-

merated in polynomial time.

IT INFRASTRUCTURE

IT infrastructure is made up of the underlying technology

products on which the SCM technologies run. It consists

of the networks, databases, and application interfaces that

support supply chain information flows and that allow

supply chain applications to communicate with other ap-

plications. These building blocks provide the key to being

able to take advantage of the many supply chain products

and services available in the marketplace.

Traditionally, a point-to-point integration structure

(Figure 4) has been used to link applications together. Al-

though there may be performance advantages in the exe-

cution of applications using this approach, this becomes

cumbersome and expensive to maintain in an environ-

ment where there are many components in the application

portfolio.

An alternative to point-to-point integration is to de-

velop an integration infrastructure (Figure 5) using a com-

mon interface technology in all applications.

A strategy for integration should be developed early in

the supply chain design cycle. Once the infrastructure has

been established, only SCM applications that can operate

within that infrastructure should be considered for inte-

gration into the system. Two approaches are discussed

below.

Figure 4: Point to point-integration structure.

Middleware

Enterprise middleware provides a common interface that

all applications can use, no matter the operating sys-

tem platform on which they run. In a message queuing

environment, a set of enterprise application program-

ming interfaces is provided for each operating system.

These interfaces are invoked by the applications to pro-

vide communication and messaging capabilities, data

transformation, routing, and application connections. In-

stead of communicating directly with other applications,

each application sends information through a “hub and

portal” (Arntzen & Shumway, 2002) directed by the mes-

sage queuing controller. The advantage of this approach

is twofold. First, all applications communicate with each

other in the same way. Second, as applications are added

or replaced, the other applications they communicate

with do not have to be modified. An example of this type

of middleware is IBM’s MQ Series product set.

Database Interface

A database interface strategy uses a common database

management system to facilitate the transfer of data be-

tween application systems. In this case, an enterprise

Figure 5: An integration infrastructure.