Domain driven simulation modeling for software design

System-theoretic modeling and simulation frameworks such as Object-Oriented Discrete-event System Specification (OO-DEVS) are commonly used for simulating complex systems, but they do not account for domain knowledge. In contrast, Model-Driven Design environments like Rhapsody support capturing domain-specific software design, but offer limited support for simulation. In this paper we describe the use of domain knowledge in empowering simulation environments to support domain-specific modeling. We show how software design pattern abstractions extend the domain-neutral simulation modeling. We applied Composite, Façade, and Observer patterns to an astronomical observatory (AO) command and control system and developed domain-specific simulation models for the system using DEVSJAVA, a realization of OO-DEVS. This approach is exemplified with simulation models developed based on an actual AO system.