SWRL is based on a combination of the OWL DL and OWL Lite sublanguages of OWL with the Unary/Binary Datalog RuleML sublanguages of RuleML. SWRL extends the set of OWL axioms to include Horn-like rules. An extension of the OWL model-theoretic semantics is also given to provide a formal meaning for OWL ontologies including rules written in an abstract syntax. The rules are of the form of an implication between an antecedent (body) and consequent (head). The intended meaning can be read as: whenever the conditions specified in the antecedent hold, then the conditions specified in the consequent must also hold.