The Semantic Web Rule Language (SWRL) is based on a combination of parts of OWL and the Rule Markup Language (RuleML) as well as DATALOG. The idea is to apply DATALOG Rules to OWL Ontologies. The Symbols and Rules are OWL Identifiers or new DATALOG Identifiers. The only problem is that the combination of Description Logics and First Order Logics Rules are although they are restricted to decidable Fragments of First Order Logic Rules, the Combination becomes undecidable.
There are Combinations that allow it to become decidable.