ConceptBase.cc is a multi-user deductive and object-oriented database system for metamodeling and method engineering. Includes a graphical client that builds upon the logic-based features of the ConceptBase,cc server. The data model is O-Telos. ConceptBase.cc can represent information at the data level (example data, traces of process executions etc.), the class level (schemas, process definitions etc.), the metaclass level (constructs of modeling languages), the meta-metaclass level (constructs for defining modeling languages), and so forth. ConceptBase.cc is developed by the ConceptBase Team at Tilburg University and University of Aachen (RWTH). ConceptBase.cc supports Linux, Solaris, and Windows. The system is distributed under a FreeBSD-style license.