The paper presents a scheme for hybrid integration of rules languages with constraints languages including but not restricted to Description Logic-based ontologies. The proposed scheme is apt for logical rule languages such as Datalog, but also opens up for rules lacking logical semantics, e.g. the XML query and transformation language Xcerpt. To reason in the integrated language, we aim at re-using and interfacing existing reasoners for the component languages. Here we show how this can be

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... mplished for integrating Datalog and Xcerpt with OWL by interfacing XSB and an Xcerpt engine with a DL reasoner, respectively. Finally, we suggest ideas on how to improve reasoning performance by allowing for more frequent interaction between the component systems.