Book excerpt: Every company must continually wrestle with the problem of deciding the right quantity and mix of products or services that it should produce as well as when and where to produce them. The problem is challenging because the decision must be made with uncertain and conflicting information about future demand, available production capacity, and sources of supply. The decision is in fact a highly complex balancing act, involving tradeoffs along many dimensions - for example, inventory targets vs. customer service levels, older products vs. newer ones, direct customers vs. channel partners - and requiring the compromise of constituents - sales, marketing, operations, procurement, product development, finance, as well as suppliers and customers - with varied objectives. The ability of a company to nimbly navigate this decision process without giving too much influence to any of the parties involved largely determines how well the company can respond to changing market conditions and ultimately whether the company will continue to thrive. This book focuses on the complex challenges of supply chain planning - the set of business processes that companies use for planning to meet future demand. Supply chain planning comprises a variety of planning processes within an organization: demand planning, sales & operations planning, inventory planning, promotion planning, supply planning, production planning, distribution planning, and capacity planning. Of course, not all companies engage in all of these planning activities and they may refer to these activities by other names but they all struggle with the on-going effort of matching demand with supply. Many textbooks address supply chain planning problems and present mathematical tools and methods for solving certain classes of problems. This book is intended to complement these texts by focusing not on the mathematical models but on the problems that arise in practice that either these models do not adequately address or that make applying the models difficult or impossible. The book is not intended to provide pat solutions to these problems, but more to highlight the complexities and subtleties involved and describe ways to overcome practical issues that have worked for some companies.