I used the jsr-94 API to create a StatelessRuleSession, registered the rule.xml file which I attached and fed in the strings "hello" and "world" as in-params. Although I declared the two rules within the attached file to belong to the same xor-group, both rules get fired upon execution: output of my test-application: [java] Starting Application [java] URL for rule file file:///C:\dev\projects\rule-test/meta/rules.xml [java] Service provider created [java] Ruleset registered [java] rule sesssion created [java] Rule ONE fired. [java] Rule TWO fired. To my understanding, only rule ONE should be fired because both rules belong to the same XOR-group. Maybe I'm missing something but I also ran tests using the xor-group attribute in combination with other attributes like salience, no-loop etc. but couldn't produce the desired effect of mutually exclusive rules.