A major goal of the H2020 Inter-IoT project isto provide a framework for seamless integration of differentInternet of Things (IoT) platforms. To allow the Inter-IoT user tointeract with those platforms, which feature their own syntax andApplication Programming Interfaces (APIs), so called bridgesare designed and implemented. For ensuring interoperability,semantics play a key role. The ontologies used by the differentplatforms need to be aligned with a central ontology. We presentthe features supported by Inter-IoT{\textquoteright}s Inter-MiddleWare layerand discuss the operation of a bridge towards a oneM2M basedplatform.