We introduce semantic reflection as an architectural concept for Intelligent Virtual Environments (IVEs). SCIVE, a dedicated IVE simulation core, combines modularity with close coupled integrative aspects to provide semantic reflection on multiple layers from low-level simulation core logic, specific simulation modules' application definitions, to high-level semantic environment descriptions. SCIVE's Knowledge Representation Layer provides the central organizing structure which ties together data representations of simulation modules, e.g., for graphics, physics, audio, haptics, or Al etc., while it additionally allows bidirectional knowledge driven access between the modules.