Abstract: Model integrated computing (MIC) is an effective and efficient method for developing, maintaining, and evolving large-scale, domain-specific software applications for computer-based systems (CBSs). On a higher level, it is possible to use MIC to develop, maintain, and evolve the meta-level tools (metamodeling environments) themselves, by modeling the metamodeling environment (meta-metamodeling). This paper documents the evolution of one metamodeling environment into another: specifically the design choices of the newer metamodeling environment with regard to the old one, and the solutions to problems that were introduced with the change.