Ruleby
Ruleby is a rule engine written in the Ruby language. It is a system for executing a set of IF-THEN statements known as production rules. These rules are matched to objects using the forward chaining Rete algorithm. Ruleby provides an internal Domain Specific Language (DSL) for building the productions that make up a Ruleby program.
FYI, if you’re in the Huntsville, AL area come hear Joe Kutner give a presentation on Ruleby at the upcoming hsv.rb meetup, taking place at BizTech on February 13th @ noon.