Supply-chain management (SCM) has three principal components: (a) creating the supply-chain network structure, (b) developing supply-chain business processes, and (c) managing the supply-chain activities. 
The supply-chain network structure consists of the member firms and the links between these firms. Primary members of a supply chain include all autonomous companies or strategic business units that carry out value-adding activities in the business processes designed to produce a specific output for a particular customer or market. Supporting members are companies that simply provide resources, knowledge, utilities, or assets for the primary members of the supply chain. For example, supporting companies include those that lease trucks to a manufacturer, banks that lend money to a retailer, or companies that supply production equipment, print marketing brochures, or provide administrative assistance.
Supply chains have three structural dimensions: horizontal, vertical, and the horizontal position of the focal company within the end points of the supply chain. The first dimension, horizontal structure, refers to the number of tiers across the supply chain. The supply chain may be long, with numerous tiers, or short, with few tiers. As an example, the network structure for bulk cement is relatively short. Raw materials are taken from the ground, combined with other materials, moved a short distance, and used to construct buildings. The second dimension, vertical structure, refers to the number of suppliers or customers represented within each tier. A company can have a narrow vertical structure, with few companies at each tier level, or a wide vertical structure with many suppliers or customers at each tier level. The third structural dimension is the company’s horizontal position within the supply chain. A company can be positioned at or near the initial source of supply, be at or near to the ultimate customer, or be somewhere between these end points of the supply chain.
Business processes are the activities that produce a specific output of value to the customer. The management function integrates the business processes across the supply chain. Traditionally, in many companies, upstream and downstream portions of the supply chain were not effectively integrated. Today, competitive advantage increasingly depends on integrating eight key supply-chain processes—customer relationship management, customer service management, demand management, order fulfillment, manufacturing flow management, procurement, product development and commercialization, and managing returns—into an effective value delivery network. 
Regarding the supply-chain management function itself, in some companies, management emphasizes a functional structure, others a process structure, and yet others a combined structure of processes and functions. The number of business processes that it is critical or beneficial to integrate and manage between companies will likely vary. In some cases, it may be appropriate to link just one key process, and, in other cases, it may be appropriate to link multiple or all the key business processes. However, in each specific case, it is important that executives thoroughly analyze and discuss which key business processes to integrate and manage. With the shift from the traditional “push” to the modern “pull” model, supply-chain management has changed—the integration of e-commerce has produced (a) greater cost efficiency, (b) distribution flexibility, (c) better customer service, and (d) the ability to track and monitor shipments.
 Lambert and Cooper (2000, January).
 Lambert , Guinipero, and Ridenhower (1998).
The best companies create supply chains that can respond to sudden and unexpected changes in markets. Agility—the ability to respond quickly and cost-effectively to unexpected change—is critical because in most industries, both demand and supply fluctuate more rapidly and widely than they used to. In fact, the best companies use agile supply chains to differentiate themselves from rivals. For instance, Zara has become Europe’s most profitable apparel brands by building agility into every link of their supply chains. At one end of the product pipeline, Zara has created an agile design process. As soon as designers spot possible trends, they create sketches and order fabrics. That gives them a head start over competitors because fabric suppliers require the longest lead times. However, the company approves designs and initiates manufacturing only after it gets feedback from its stores. This allows Zara to make products that meet consumer tastes and reduces the number of items they must sell at a discount. At the other end of supply chain, the company has created a superefficient distribution system. In part because of these decisions, Zara has grown at more than 20% annually since the late 1990s, and its double-digit net profit margins are the envy of the industry.
Agility and resiliency have become more critical in recent years because sudden shocks to supply chains have become more frequent. The terrorist attack in New York in 2001, the dockworkers’ strike in California in 2002, and the SARS epidemic in Asia in 2003, for instance, disrupted many companies’ supply chains.
Agility and resiliency help supply chains recover more quickly from such sudden setbacks. When, in September 1999, an earthquake hit Taiwan, shipments of computer components to the United States were delayed by weeks and, in some cases, by months. Most computer manufacturers, such as Compaq, Apple, and Gateway, could not deliver products to customers on time and incurred losses. One exception was Dell. The company changed the prices of PC configurations overnight to steer consumer demand away from hardware built with components that were not available to machines that did not require those parts. Dell could do this because it had contingency plans in place. Not surprisingly, Dell gained market share in the earthquake’s aftermath. 
Supply-chain agility and resilience no longer imply merely the ability to manage risk. It now assumes that the ability to manage risk means being better positioned than competitors to deal with—and even gain advantage from—disruptions. Key to increasing agility and resilience is building flexibility into the supply-chain structure, processes, and management. 
 Lee (2004, October).
 Sheffi (2005, October).