Can we contribute to developing a consistent terminology and, to some extent, an acceptable ontology in the rapidly expanding field of human systems integration (HSI)? We often define HSI as a process and a product at the confluence of several areas, such as systems engineering, human factors and ergonomics, information technology, and specific sectors, such as aerospace, health, and energy. It is a broader transdisciplinary field in our increasingly complex human-machine world that focuses on integrating technology, organizations, and people within a complex sociotechnical system throughout its life cycle. Therefore, HSI is no longer a question of usability and user interface design once a complex machine is technologically developed, but also about considering people and organizations early on in the design and development processes. Indeed, rooted in industrial engineering research and operational worlds, HSI requires a deeper foundation based on an epistemological approach. This assertion is even more crucial today as technology has become predominantly digital, and, more specifically, the concept of the digital twin is emphasized because it has become essential to support model-based HSI. In other words, software-based assistant systems are replacing traditional tools. Therefore, appropriate social-cognitive (multi-agent) models and methods are helpful throughout the life cycle of contemporary sociotechnical designs to account for the complexity and tangibility of their human-centered context-sensitive architectures, combining procedural and declarative knowledge. By considering these reasons, this article provides a set of fundamental axioms, some theoretical abstractions, and valuable practical models, which are presented and illustrated through the lens of an evolutionary HSI ontolog