Modern critical systems bear great responsibilities and face escalating challenges. Distributed systems for critical applications are costly and time-consuming to develop and to certify. Since there is little automated support for early assurance that a system faithfully implements its architectural design and satisfies its requirements, qualification testing and certification processes often reveal deficiencies that require costly late changes. MILS provides compositional system construction and assurance, leveraging individually developed and assured components to predict and assure the properties of composite systems. By providing a modular high-assurance platform and a framework for the certification of systems built on that platform. MILS reduces the cost and time for development, certification, and maintenance of dependable systems.