labor and materials flowing smoothly into and through the value stream. A focus on mura reduction and flow may bring benefits that would be otherwise missed by focus on muda (the Japanese word for waste) alone. The former necessitates a system-wide approach whereas the latter may produce suboptimal results and unintended consequences. For example, a software development team may produce code in a language familiar to its members and which is optimal for the team (zero muda). But if that language lacks an API standard by which business partners may access the code, a focus on mura will expose this otherwise hidden source of waste. Pull/demand system Pull (also known as demand) systems are themselves closely related to the aforementioned flow concept. They contrast with push or supply systems. In a pull system, a pull is a service request. The initial request is from the customer or consumer of the product or service. For example, a customer initiates an online purchase. That initial request in turn triggers a subsequent request (for example, a query to a database to confirm product availability), which in turn triggers additional requests (input of the customer's credit card information, credit verification, processing of the order by the accounts department, issuance of a shipping request, replenishment through the supply-chain management system, and so on). Push systems differ markedly. Unlike the “bottom-up,” demand-driven, pull systems, they are “top-down,” supply-driven systems whereby the supplier plans or estimates demand. Push systems typically accumulate large inventory stockpiles in anticipation of customer need. In IT, push systems often introduce waste through an over-abundance of “just-in-case” inventory, incorrect product or service configuration, version control problems, and incipient quality issues. Implementation Implementation begins with identification and description of one or more IT value streams. For example, aided by use of interviews and questionnaires, the value stream for a primary value stream such as a point-of-sale business service may be described as shown in Table 2. Table 2 suggests that the Executive Vice President (EVP) of Store Operations is ultimately responsible for the point-of-sale business service, and he/she assesses the value of this service using metrics such as CAPEX, OPEX, and check-out speed. The demand pulls or purposes for which the EVP may seek these metrics might be to conduct a budget review or undertake a store redesign. Formal service-level agreements (SLAs) for provision of the business service may monitor transaction speed, service continuity,