R1 is a rule-based system that has much in common with other domain-specific systems that have been developed over the past several years. It differs from these systems primarily in its use of Match rather than Generate-and-Test as its central problem solving method; rather than exploring several hypotheses until an acceptable one is found, it exploits its knowledge of its task domain to generate a single acceptable solution. R1’s domain of expertise is configuring Digital Equipment Corporation’s VAX-11/780 systems. Its input is a customer’s order and its output is a set of diagrams displaying the spatial relationships among the components on the order; these diagrams are used by the technician who physically assembles the system. Since an order frequently lacks one or more components required for system functionality, a major part of R1’s task is to notice what components are missing and add them to the order. R1 is currently being used on a regular basis by DEC’s manufacturing organization.