# Metaverse Architectures: A Comprehensive Systematic Review of Definitions and Frameworks
## 4 Discussion
### Metaverse Architecture
#### 4.2.2 Conceptual Similarities Across Metaverse Architectures  
This section examines the conceptual similarities among three-layer, four-layer, and five-layer metaverse architectures. The accompanying figures visually illustrate how these frameworks, despite differences in structural detail and terminology, frequently converge on functionally equivalent components. Each comparison underscores shared core functionalities, including user interaction, computational processing, and infrastructure support. Figures 6-8 illustrate the metaverse architecture, representing three distinct architectural models: the three-layer, four-layer, and five-layer architectures, along with their interrelations. The illustration aims to highlight the hierarchical structure of various architectures and the conceptual commonalities between levels that perform analogous duties but are designated differently among architectures. Bidirectional arrows point to areas of conceptual overlap or functional equivalency by indicating layers that carry similar purposes in the comparative structures. The three-layer and four-layer architectures, as shown in Figure 6, exhibit significant structural similarities. Both frameworks establish a fundamental infrastructure layer responsible for processing, communication, storage, and the integration of enabling technologies. Each architecture utilises blockchain to facilitate secure digital ownership, economic transactions, and trust management inside the virtual ecosystem. A specific layer in both models enables interaction between the physical and virtual realms, referred to as \"Interactivity\" in the three-layer architecture and manifested through the metaverse engine and virtual world in the four-layer architecture. Moreover, both architectures prioritise immersive user experiences by utilising technologies such as virtual reality, augmented reality, and spatial computing, and depend on digital representations to facilitate avatar-based or system-level interactions. Ultimately, each framework facilitates a virtual environment or ecosystem layer that fosters social, cultural, and economic activities, supporting enduring and multi-user digital communities. These common traits demonstrate a fundamental congruence in design principles, emphasising interoperability, scalability, and user-centric engagement across platforms. Figure 6: Layer mapping between three-layer and four-layer architecture. A comparative analysis of the three-layer and five-layer architecture, as shown in Figure 7, highlights several patterns of conceptual equivalence. Both architectures include an infrastructure layer that serves as the technical foundation of the metaverse, providing essential computing and networking resources. In both architectures, blockchain technology, at a fundamental level, provides secure digital ownership, trustless transactions, and the development of decentralised virtual economies. The three-layer approach incorporates blockchain in the infrastructure layer to enable smart contracts and distributed governance, whereas the five-layer architecture integrates it into the metaverse engine to enhance asset management and ensure transparent economic exchange. In the three-layer architecture, the ecosystem layer consolidates functions related to user engagement, application services, and social interaction. In contrast, the five-layer architecture adopts a more distributed approach, separating these functions across three distinct layers: the digital life layer, the interconnected virtual worlds layer, and the metaverse engine layer. Together, these layers manage immersive environments, real-time interactivity, and content rendering. Additionally, the five-layer architecture explicitly includes a human society layer, which emphasises user-centric aspects that are present, but not formally defined, in the three-layer architecture. Similarly, the four-layer and five-layer architectures exhibit closely related functional characteristics in Figure 8. The alignment of infrastructure components is once again evident.