Event Condition Action rule engines have been developed for some time now. Theycan respond automatically to events coming from different sources. Combination ofdifferent event types may be different from time to time and there for it is hard todetermine how the rule engine executes its rules. Especially when the engine is givena large rule set to work with. To determine the behavior is to run tests on the ruleengine and see the final results, but if the results are wrong it can be hard to see whatwent wrong. ruleViz is a program that can look at the execution and visually animatethe rule engine behavior by showing connections between rules and composite events,making it easier for the operator to see what causes the fault. ruleViz is designed toembrace Human Computer Interaction (HCI) methods, making its interfaceunderstandable and easy to operate.