Many semantic web applications require support for knowledge representation and inference over a federation of multiple autonomously developed ontology modules allowing selective partial reuse of knowledge, based on a well-coordinated context-sensitive semantics. Federated  or  is a modular description logic, each of whose modules is roughly an  ontology  with inverse roles and with an epistemic operator).  supports importing of both concepts and roles across modules and contextualized interpretation of all logical connectives. Moreover, it allows non-monotonic reasoning, formalization of procedural rules as well as various forms of sophisticated query formulation, as does its single-module counterpart  To show that this contextualized epistemic federated description logic is decidable and to evaluate the complexity of the corresponding satisfiability problem, a sound and complete reduction to the description logic  modeled after a corresponding reduction from  to  is provided.