—Interoperability is generally defined as the ability to exchange data and to make use of these data within the receiving system. For information technology systems this definition makes perfect sense, as the exchange of data via common protocols in a shared infrastructure is the only way to make systems work with each other. For simulation systems, however, the exchange and use of data is necessary, but not sufficient. Simulation systems execute models, which represent purposeractions and simplifications of a task-oriented reality. Meaningful interoperation of two systems requires the alignment of concepts represented in the underlying models. Composability ensures the alignment of these concepts by ensuring the consistent representation of interpretations of truth among all participating systems. The presented work uses a branch of mathematics called model theory to investigate definitions of interoperability and composability and provides the implications for verification and vali...