Copyright 2011-2012, The RuleML Initiative.
This document is a primer on RuleML 1.0 (Rule Markup Language, which has also become a Rule Modeling Language and a Rule MetaLogic). RuleML is being used for sharing rule bases in XML and publishing them on the Web. RuleML constitutes a layered family of rule sublanguages of which this primer focuses on Datalog and Horn logic. The XML serialization of these sublanguages will be visualized with OrdLab trees, developing an example, from the business policy domain, about discount policy.
RuleML as a non-profit organization has been the driver of Web rule research, building interoperation bridges between other Web rule languages, partnering with standards bodies, and working with industry.