# Context-Aware Systems Architecture in Industry 4.0: A Systematic Literature Review
## 5 Analysis and Discussion
### Architecture Technologies, Norms, Models, and Standards
#### 5.3.3 Architecture Standards
[93], and [PERSON] et al. [74] to provide services to external entities, minimising the complexity resulting from heterogeneity. On the other hand, [PERSON] et al. [77] proposed an architecture capable of offering contextual services to third parties via RESTful, intending to make information available. Similarly, [PERSON] et al. [39] implemented services for applications in the business layer, and [PERSON] et al. [73] integrated the sensor layer and the situation recognition layer, demonstrating the versatility and applicability of the SOA and its associated technologies in optimising communication and interoperability in complex systems. In a highly distributed context, incorporating agent-based technologies emerges as an innovative control paradigm that can efficiently overcome field challenges. As elucidated by [PERSON] et al. [80], this approach is beneficial in managing the complexities intrinsic to personalised systems. In addition, the modularity and distribution inherent in this pattern provide the essential abstraction for the delineation of various operational states, mirroring the system's behaviour and facilitating adaptation to the heterogeneity of the physical environment. CPS offers a balance of intelligence capabilities for data analysis and decision-making at different levels. In this context, implementing autonomous agents adds the ability to make decisions and ignores the need to consider fixed hierarchical structures [91]; see also [PERSON] et al. [55]. Additionally, to enhance cooperation between the components of an IIoT network, a practical approach is to conceive the network as a distributed cooperative system based on agents. Furthermore, according to [PERSON] et al. [74], agents promote the self-configuration and modification of the system, providing a more comprehensive range of decisions to respond to the external environment. To address the inherent challenge of interoperability between interconnected resources, the architecture proposed by [PERSON] et al. [55] applies the publisher-subscriber standard. This approach uses a unified data model to formulate subscription requests and subsequent notifications. The research carried out by [PERSON] et al. [91] evaluated the implementation of this standard to facilitate the uninterrupted receipt of relevant information, with a view to initiating specific actions reactively or proactively. This procedure aims to optimise frequently occurring asynchronous interactions, helping to reduce the volume of messages exchanged. [PERSON] et al. [80] provide stakeholders with a negotiation mechanism under the publisher-subscriber scheme. In addition, adopting communication protocols such as the WebSocket-based Message Bus [90] and MQTT [39] integrates the publishing and subscription functionality. Finally, as another pattern identified, microservices reduce the granularity and offer greater flexibility compared to the SOA. In distributed applications, [PERSON] et al. [86] suggest using microservices coupled with docker containers because this granularity makes it easier to model, develop, and maintain applications. [PERSON] et al. [84] added microservices to support control functionalities and associated each microservice with a service from the logical and physical layers.