Some years ago, I watched an elementary school teacher use a simple but interesting exercise to illustrate the interconnections among the various components of the environment. In the lesson, each student represented some part of an ecosystem: sun, rain, soil, predator, prey, or plant. As the students named a connection from part to part—sunshine leads to evaporation, which leads to clouds, which leads to rain, which leads to plant growth, which leads to food for herbivores, and so on—they stretched strings of yarn from one person to the next, representing each connection.

Before long, a complex web of yarn stretched across the room. The teacher had successfully demonstrated an important lesson in a graphic way.

I have often thought of that class when considering supply chain management—the raison d'etre for this publication. The term "supply chain" itself evokes an image of interconnections among all the players from source to final consumption (at least in theory). Or as one General Motors executive has said, he looks forward to the day when a customer orders a Cadillac with leather seats, and the cow in the field gets nervous.

Clear enough. Yet the term "supply chain" is really an intentional simplification of the way complex business processes work. More accurately, it is like the classroom of 12-yearolds holding on to a web of yarn. For it is indeed a tangled web we weave when we venture to link function to function and participant to participant. When something shifts in one part of the supply chain, the ripples may well be felt elsewhere, in unexpected places and in unexpected ways.

In the past, I have used the metaphor of an orchestra conductor to describe the work of supply chain managers. But it now seems to me that the image doesn't quite work. In an orchestra, the strings, brass, reeds, and percussion are all on the same stage, all literally on the same page, and all have the same goal of delivering to their "customer"—the audience—a compelling, moving, and flawless Beethoven or Mozart or Britten. But participants in supply chains—or supply webs, if you will— can and often do have different agendas that do not always mesh. As in the science lesson, the predator and the prey may be part of the whole web of nature, but that doesn't mean the prey is happy about the arrangement. So, too, suppliers may meet the requirements of a big customer while bitterly resenting the terms.

Ensuring that supply chain design meshes with the goals of even a single organization can be daunting because business, economic, and political conditions shift continually. No supply web is ever a static thing, and keeping its parts connected is the supply chain manager's perpetual challenge.

Our hope is that what you have read in this publication helps you meet that challenge by illuminating the strands in the web, how they interconnect, and how to make them stronger.