# Metaverse Architectures: A Comprehensive Systematic Review of Definitions and Frameworks
## 4 Discussion
### Metaverse Architecture
#### 4.2.1 Hierarchical Structure of the Metaverse Architectures
Metaverse Engine: The metaverse engine orchestrates inputs from physical and virtual environments to create immersive experiences. Using AR / VR interfaces, haptic technologies, and the Tactile Internet, it is able to improve user interaction. Interoperability standards ensure consistency across platforms. Digital twin systems replicate physical assets in real-time, while AI manages functionalities like 3D rendering and avatar creation. Blockchain technologies support decentralised ownership and asset management. The engine also incorporates a virtual economy layer for transactions and content monetisation. These components collectively enable the creation of dynamic, responsive, and persistent digital environments. 1. Infrastructure: The infrastructure layer is crucial for enabling efficient access by distributing computing resources closer to end-users, which significantly enhances user experiences through low latency and high-speed data transfer. It is designed to support high-density networks capable of managing the ever-increasing data demands of modern applications. By employing advanced communication technologies, this layer enhances bandwidth and overall efficiency, while a multi-layered computing approach balances performance with scalability. Basic tasks can be processed directly on user devices, allowing complex tasks to be offloaded to distributed servers, effectively optimising resource usage. Furthermore, AI-driven optimisation techniques are applied to improve efficiency and reduce network load. Security is paramount, ensuring the management and verification of digital assets while also supporting peer-to-peer transactions and interoperability across various virtual environments. This infrastructure layer facilitates cross-platform accessibility and resource-sharing, creating a cohesive and efficient distributed ecosystem. 3. Five-Layer Architecture: The five-layer metaverse architecture is a detailed and flexible framework intended to include the entire range of virtual environment creation and engagement. Figure 5 illustrates that this architecture comprises the following layers. Figure 5: The five-layer metaverse architecture, expanding the structure with human society, interconnected virtual worlds, and digital life layers. 5. Digital Life: The digital life layer represents the diverse virtual experiences, services, and economies within the metaverse. It encompasses multiple interconnected sub-metaverses, each offering unique digital environments, applications, and services that cater to various user needs, such as gaming, social networking, education, virtual commerce, and digital entertainment. 4. Interconnected Virtual Worlds: The interconnected virtual worlds are an expansive digital landscape that comprises multiple interconnected distributed virtual worlds, often referred to as sub-metaverses. Each of these sub-metaverses caters to specific interests by providing a range of virtual goods and services, including gaming, social networking, online museums, and virtual concerts. Users can explore diverse environments within these sub-metaverses, immersing themselves in unique game scenes or navigating vibrant virtual cities. Central to the experience are avatars, which act as digital representations of human users, allowing them to engage and interact within these virtual realms. 3. Metaverse Engine: The metaverse engine merges physical, digital, and virtual elements into a cohesive experience, leveraging big data to generate and continuously update expansive virtual worlds. With the capability for real-time rendering, users can seamlessly interact between their physical surroundings and the digital landscape. This immersive environment is supported by technologies such as extended reality, human-computer interaction (HCI), and brain-computer interfaces (BCI), allowing individuals to control avatars through their senses and physical movements. This multifaceted platform not only facilitates gaming and social interactions but also enables virtual commerce.