## 2 Related Work  
In this section, we present some Industry 4.0, CPPS, or IIoT (reference or concrete) architectures proposed in the literature, and analyze them based on different criteria. The objective of this analysis is to verify the ability of these architectures to support system self-reconfiguration. The considered analysis criteria were:  
1. Goal of the architecture--as the objectives of the proposed architectures may be diverse [11; 12], such as design, deployment, reconfiguration, and so on, it is important to identify those that are designed to favor reconfiguration;
2. Resources considered--to support reconfiguration, all production resources involved in the reconfiguration must be taken into account by the architecture (e.g., machinery, raw materials, energy, personnel);
3. Scope of the architecture--the trigger for the reconfiguration may be internal (e.g., breakdown, absence) or external (e.g., change in customer requirements, failure of a supplier or subcontractor). Reconfiguration can impact internal entities (e.g., machines, staff), as well as external actors (e.g., customers, subcontractors). It is, therefore, essential that the scope of the architecture includes those entities and actors that may cause or be affected by reconfiguration;* Level of detail--the level of detail of the description of entities/actors must be sufficiently rich to provide the necessary information for a reconfiguration algorithm. However, it should not be too detailed, as this could make it unnecessarily complex;
* Exchanged flows considered--interaction between entities/actors takes place not only through the exchange of data/information, but also through the exchange of material and energy flows. It is, therefore, essential that these different flows are considered by the architecture;
* Flow exchange methods/protocols--different exchange methods/protocols exist. The aim here is to identify those that are used or recommended by the different architectures;
* Mode of decomposition--two main modes of decomposition exist, functional decomposition and physical decomposition [9], the latter being more suitable for reconfiguration processes [10];
* Type of integration--the proposed architectures generally adopt a hierarchical representation and assign the entities/actors of the system to the different levels. Interactions can take place not only between entities/actors of the same level (horizontal integration), but also between entities/actors belonging to different levels (vertical integration). As reconfiguration can modify both types of integration, a hierarchical architecture must explicitly support them;  
The aim here is not to exhaustively describe the state-of-the-art of existing architectures, but to identify the main characteristics of the existing families of architectures to illustrate our comments on their capacity to support self-reconfiguration.  
Among the existing architectures, we can distinguish between those that were conceived as a standardization industry reference architecture, which have acquired the status of a national (or even international) standard, and the many other architectures, proposed mainly by academics and which are more or less popular. Among the latter, we can distinguish holonic and non-holonic architectures. [PERSON] et al. [11] carried out a review of several nonholonic architectures, while a survey of holonic architectures can be found in the work of [PERSON] et al. [12].  
Among standardization architectures for Industry 4.0, the RAMI 4.0 (Reference Architecture Model Industry 4.0) and IIRA (Industrial Internet Reference Architecture) architectures are the most widely known and used [11].