Modularity and reusability are key features driving digital twin simulation — so how do we create real interoperability that ensures a meaningful and long lasting digital twin infrastructure? Presented at I/ITSEC 2023, this paper, titled The Digital Twin Encapsulation Standard: An Open Standard Proposal for Simulation-Ready Digital Twins, presents a path forward that ensures full reusability of digital twins in any operational context, while avoiding the possibility of vendor lock-in.