TABLE OF CONTENTS A supply chain system (supply chain, for short) is a network that mediates the flow of entities involved in a product life cycle, from production to vending (Simchi-Levi et al. [2003]). Such a network consists of nodes and arcs. Nodes represent suppliers, manufacturers, distributors, and vendors (e.g., retail stores), as well as their inventory facilities for storing products and transportation facilities for shipping them among nodes. Arcs represent routes connecting the nodes along which goods are transported in a variety of modes (trucking, railways, airways, and so on). From a sufficiently high vantage point, supply chains have essentially a feed-forward network structure, with upstream and downstream components arranged in echelons (stages), such that raw materials, parts, products, and so on flow downstream, payments flow upstream, and information flows in both directions. However, there are supply chains where entity flows may not be strictly directional because products may be returned for repair or refund. The key supply chain echelons are as follows:
The supply echelon feeds raw material or parts to the manufacturing operations.
The production echelon converts raw material and parts to finished product.
The distribution echelon consists of a distribution network (warehouses, distribution centers, and transportation facilities) that moves finished products to vendors.
The vendor echelon sells products to end-customers.
In practice, the complexity of supply chains spans a broad range from simple supply chains where each echelon is a single node, to complex ones where each echelon is itself a...
