The nationwide ARPA Network, composed of widely separated computers that vary in make, model, size, speed, and other hardware and software features, was set up to examine the intercommunication problems that arise in resource sharing among dissimilar, geographically separate systems. The Data Reconfiguration Service (DRS) is a Network experiment involving communication between two autonomous but cooperating processes with different input/output interfaces. A DRS user defines forms that specify the desired data transformations in order for each process to receive data in an acceptable format. The two processes then communicate as if they were directly connected. The DRS, however, monitors their dialog and performs the user-specified transformations on data passing between them. This report describes the syntax and semantics of forms. Examples are given of simple representative uses of the DRS, e.g., field insertion, field deletion, variable length string processing, string length computation, field transposition, and character packing and unpacking. 31 pp. Ref.