Hybrid simulation: when to combine methods
Combine DES, agent-based modelling, or system dynamics only when different parts of the problem need different representations.
A hybrid model uses two or more simulation approaches because different parts of the problem need different representations. Common combinations include discrete-event simulation with agent-based modelling, or discrete-event simulation with system dynamics.
A hospital can use discrete events for patient queues and services while agents represent staff or patients whose behavior changes with local conditions. A supply-chain model can use discrete events inside facilities and system dynamics for slower market feedback.
If one method already answers the question, adding another method only adds interfaces, assumptions, and tests.
Write down the state or events exchanged between the parts, when that exchange happens, and which side owns each variable. Ambiguous ownership is a common source of double counting and timing errors.
Verify each model component on its own, then test the interface with small cases. Validation must cover the combined behavior because a sensible DES model and a sensible ABM can still interact badly.