*Article* **Ontology-Based Process Modelling-with Examples of Physical Topologies**

**Heinz A Preisig**

> Department of Chemical Engineering, Norwegian University of Science and Technology, 7491 Trondheim, Norway; Heinz.Preisig@chemeng.ntnu.no

**Abstract:** Reductionism and splitting application domain into disciplines and identify the smallest required model-granules, termed "basic entity" combined with systematic construction of the behaviour equations for the basic entities, yields a systematic approach to process modelling. We do not aim toward a single modelling domain, but we enable to address specific application domains and object inheritance. We start with reductionism and demonstrate how the basic entities are depending on the targeted application domain. We use directed graphs to capture process models, and we introduce a new concept, which we call "tokens" that enables us to extend the context beyond physical systems. The network representation is hierarchical so as to capture complex systems. The interacting basic entities are defined in the leave nodes of the hierarchy, making the overall model the interacting networks in the leave nodes. Multi-disciplinary and multi-scale models result in a network of networks. We identify two distinct network communication ports, namely ports that exchange tokens and ports that transfer information of tokens in accumulators. An ontology captures the structural elements and the applicable rules and defines the syntax to establish the behaviour equations. Linking the behaviours to the basic entities defines the alphabet of a graphical language. We use this graphical language to represent processes, which has proven to be efficient and valuable. A set of three examples demonstrates the power of the graphical language. The Process Modelling framework (ProMo) implements the ontology-centred approach to process modelling and uses the graphical language to construct process models.

**Keywords:** model-based; computational engineering; process simulation; digital twin
