Book excerpt: This book constitutes the refereed proceedings of the International RuleML Symposium on Rule Interchange and Applications, RuleML 2008, held in Orlando, FL, USA, in October 2008 - collocated with the 11th International Business Rules Forum. The 10 revised full papers and 10 revised short papers presented together with 2 demo papers and the abstracts of 3 keynote lectures were carefully reviewed and selected from 35 submissions. The papers are organized in topical sections on rule engineering, rule-based methodologies and applications in policies, electronic contracts and security, rule representation languages and reasoning engines, rule-based methodologies and applications in distributed and heterogeneous environments, natural-language and graphical rule representation and processing, as well as exemplary contributions to the RuleML-2008 challenge.