High Quality Content by WIKIPEDIA articles! The R1 (later called XCON, for eXpert CONfigurer) program was a production-rule-based system written in OPS5 by John P. McDermott of CMU in 1978 to assist in the ordering of DEC`s VAX computer systems by automatically selecting the computer system components based on the customer`s requirements. The development of XCON followed two previous unsuccessful efforts to write an expert system for this task, in FORTRAN and BASIC).