or even patients in beds lined up in the halls. In the factory, queues are called inventory, sometimes neatly stacked in warehouses, sometimes piled up in front of machines or assembly line, waiting their turn. Each worker requires their own queue of parts, and to the factory operations expert, queues— inventory—is something to be minimized, for any part in a queue is considered idle investment.
Buffer hunting is an engaging sport. You will find them all over, even in the most unexpected places. Once your mind has been tuned to the concept, you cannot escape them. In manufacturing operations, inventory is considered waste, and the modern trend toward “pull” systems and “lean manufacturing” is an attempt to eliminate, or at least reduce, the cost of inventories of material paid for but unused, stacked up in warehouses or factory floors awaiting its turn. The goal of pull systems is to minimize inventory, for as soon as an item is used, it “pulls” the next one into the waiting area. It doesn’t take much thought to recognize that this is very difficult to do perfectly, but the philosophy allows dramatic reduction in inventory.
We can see buffers in operation almost everywhere. For example, when I walk into a dining room and see the food waiting to be dispersed to the guests, these are inventories of food, buffers. Even when eating from a plate heaped with food, the food not yet in the mouth is inventory, a buffer that makes it easy to select from the preferred order-ings at the eater’s own pace.
I once experienced an
inventory-free eating place:
completely pull-driven. I was at an expensive tempura restaurant in Japan, seated directly in front of the chef. The chef would ready a tempura piece of fish, vegetable, whatever, and carefully watch me. Each piece was made to order, fried and placed on my plate precisely when I was ready to lift it to my mouth. But even here, there were inventories: food already prepared and coated with tempura mix, hot oil awaiting the introduction of the next food morsel, a plate to hold the food, even if only for a few seconds, and, for that matter, an inventory of eaters. The eight of us sitting in front of the chef constituted an inventory of eaters, where the chef continually watched to see which diner was ready for the next mouthful. You can see why such a restaurant would have to be expensive.
Interaction design is about interfaces, which means it is about synchronizing the events of different systems, about memories, buffers, queue, and waiting rooms. Waiting is an unavoidable component of interfaces, an unavoidable part of life.
ABOUT THE AUTHOR Don Norman wears many hats, including cofounder of the Nielsen Norman Group and director of a dual-degree MBA-plus engineering program in design and operations at Northwestern University, a curriculum devoted to decreasing inventories and queues. His latest book is The Design of Future Things. He lives at www.jnd.org.
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May + June 2008
DOI 10.1145/1353782.1353790
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