Systems can exchange data successfully and still fail to understand one another. Metadata provides the context needed to interpret information consistently, making semantic interoperability an architectural concern rather than simply an interface problem.

Adding APIs, adapters, and integration layers to legacy defense simulations doesn't automatically make them data-centric. When data assumptions remain embedded in platform architectures, modernization can preserve the very interoperability problems it was intended to solve.

Modular and composable systems are often treated as interchangeable, but they represent different architectural approaches. Understanding the distinction matters when designing systems for interoperability, reuse, adaptability, and long-term evolution.