The 2009 International Symposium on Rule Interchange and Applications (RuleML 2009), collocated in Las Vegas, Nevada, with the 12th International Business Rules Forum, was the premier place to meet and to exchange ideas from all ?elds of rules technologies. The aims of RuleML 2009 were both to present new and interesting research results and to show successfully deployed rule-basedapplications.This annualsymposium is the ?agshipevent of the Rule Markup and Modeling Initiative (RuleML). The RuleML Initiative (www.ruleml.org) is a non-pro?t umbrella organi- tion of several technical groups organized by representatives from academia, industry and public sectors working on rule technologies and applications. Its aim is to promote the study, research and application of rules in heterogeneous distributed environments such as the Web. RuleML maintains e?ective links with other major international societies and acts as intermediary between v- ious 'specialized' rule vendors, applications, industrial and academic research groups, as well as standardization e?orts from, for example, W3C, OMG, and OASIS. To emphasize the importance of rule standards RuleML 2009 featured, besides a number of tutorials on various rule aspects, a tutorial and a workshop dedicated to the newly released W3C Rule Interchange Format (RIF).