## 2 Related Works and Gap Analysis  
In recent years, the life cycle management of products and solutions for Industry 4.0 has been characterised by the necessity to follow the evolution from systems to systems of systems, with an increase in complexity of adopted architectures, technologies, involved stakeholders, and requiring a new model for the engineering process. ISO/IEC/IEEE 21839 defines SoS as a \"set of systems or system elements that interact to provide a unique capability that none of the constituent systems can accomplish on its own\" [20]. A constituent system is an autonomous, distributed, and independent system, having its own EP, its own resources, its own goals, being operational and managerial independent, and interacting within the SoS with other constituent systems to provide the unique capabilities and features of the SoS. SoS evolves by adding, removing, and modifying the constituent systems, which always cooperate, coordinate, and adapt to achieve the SoS goals and to provide additional features, capabilities, and functionalities to the SoS, which are unavailable in the constituent systems. In the electronic components and system domain, a constituent system of a system of systems is defined as a set of embedded hardware hosting software designed to perform a particular task or solve a specific problem [21; 22]. In the SoS, each constituent system is considered a \"black box\". It remains operational and managerial autonomous and/or independent, relying on its own hardware, software, and networking resources, and remains focused on its own goals. According to [PERSON] and [PERSON], the SoS must satisfy five characteristics: (i) the operational independence of constituent systems; (ii) the managerial independence of constituent systems; (iii) geographical distribution; (iv) emergent behaviour; and (v) evolutionary development processes [23; 24]. Life cycle management of systems of systems requires a further improved engineering process model to properly describe and support the data flowing through systems, stakeholders, value chains and engineering phases. In this context, SOA principles help tackle interoperability issues of large-scale automation systems, where information exchange is implemented by systems providing and consuming services [25]. Another aspect to be considered is the method used to represent the links between the different phases and the synergies between the involved stakeholder, where a graphical notation should be preferred to the textual prescription, improving the clarity of the model and simplifying its adoption [26]. The definition of a system of systems project managed with an SOA-based paradigm represents an evolution of the approaches currently adopted to model the implementation of the digital thread that is fundamental in managing the product data in all the life cycle phases of products [27; 28]. The structure of the EP and the information management system can be modelled with an ontology. In this regard, many standards have already been adopted in the industry domain, e.g., IEC 10303 [29], IEC 62264 [30], ISO 15926 [31], STEP-based ontology [32], Building Information Model (BIM) [33], and ISO/IEC 81346 [34]. In Appendix A, we provide an overview of the main standards mentioned here. The standard ISO/IEC 81346 specifies that for studying objects and their relations, it may be helpful to look at them from different perspectives, highlighting various aspects of the objects and relations. This standard focuses on the three aspects of function, product, and location, although the design is intended to be capable of addressing other viewpoints, as well as to provide a guideline for the main engineering process phases that can be adopted to build the life cycle management models of objects to be manufactured [35].