The rise of Industry 4.0 has spurred a growing need for smart, interconnected production systems and supply chains in manufacturing. In this context, the seamless integration of Manufacturing Operations Management (MOM) practices is crucial for ensuring operational efficiency, product quality, and regulatory compliance across the manufacturing life-cycle. This paper presents a formal foundation for the Object-Oriented Event-Graph (OOEG) language, which aims to enable efficient simulation within the MOM architecture. At the core of this work is the proposal and formal definition of a new OOEG language, named Refinement Calculus for Object-Oriented Event-Graph (rCOE), and we explore the language’s operational semantics. This rigorous semantics specification provides a solid theoretical underpinning for the OOEG language, facilitating precise formalization and simulation of complex manufacturing processes. To demonstrate the practical applicability of the proposed approach, we present a real-world case study within the aviation manufacturing domain, focusing on the partial assembly phase.