Critical Chain: A Business Novel

by Eliyahu M. Goldratt

humps between each two soldiers. "Johnny," Jim says, "can't we regard these humps as queues before machines?" "That's exactly what they are." "Let's not talk inventory," I impatiently say. "Let's talk time." "Go ahead." Johnny is very patient. "If this work center has a problem," I point arbitrarily to one of the soldiers, "then the hump represents the time that the next soldier can still work before he will have to stop. In a way," I slowly say, "these humps represent the protection a work center has. Protection against problems occurring upstream." "You could say so," Johnny agrees. "They represent safety." "Safety. Safety. You are right. Here is the connection to projects, don't you see?" Y-E-S! "I told you that we have to relate to inventory as representing time. In production we protect a work center with inventory, in projects we protect a step with safety time." "I see what you mean," Jim comments, "and I agree. Still I think that there is a difference. In projects the situation is worse."