One of the most experienced suppliers of high–performance rule–based systems, Production Systems Technologies (PST) is a spin–off of Carnegie–Mellon University. PST was founded in 1983 by Dr. Charles Forgy, inventor of the Rete algorithm, and the principal designer of OPS5, the language in which the first commercially successful expert system was written.

The OPSJ rule engine from PST is 100% Java. OPSJ is implemented using the proprietary Rete II algorithm, and it has been shown in independent tests to run one to two orders of magnitude faster than other Java engines on complex rule bases. The speed and small footprint of OPSJ have made it a popular choice for embedded applications. OPSJ is used as the rule engine in a number of commercial products.