# Metaverse Architectures: A Comprehensive Systematic Review of Definitions and Frameworks
## 2 Methodology
### Systematic Literature Review  
A systematic literature review was undertaken to explore existing definitions and architectural models of the metaverse. Relevant studies were identified through the Google Scholar database, employing search terms including \"Metaverse\", \"Metaverse definition\", \"Metaverse requirements\", and \"Metaverse architecture\". To ensure relevance, only peer-reviewed articles published in English between 2013 and 2025 were considered.  
The selection procedure is detailed Table 1, which outlines the inclusion and exclusion criteria, and Figure 1, which presents the screening process following PRISMA flow diagram guidelines [59]. A total of 237 records were initially identified. Following the removal of 6 duplicates and 7 records for other reasons (non-English language), 224 records were screened. After reviewing abstracts and titles, 202 reports were selected for retrieval, with 10 being non-retrievable (lack of full-text availability). A full-text review was conducted on 192 reports, leading to the exclusion of 89 studies that did not satisfy the inclusion criteria (absence of definition or architectural discussion).  
From the 103 studies included in the final review, two focused subsets were extracted for thematic analysis. The first subset comprised 33 studies that contained explicit definitions of the metaverse. In this study, a metaverse definition is understood as a formal conceptualisation of the term \"metaverse\", articulated with sufficient conceptual clarity to support thematic comparison. Studies were included in this subset based on the following criteria: (1) the presence of clearly defined conceptualisations of the metaverse, located in the abstract, introduction, or a dedicated definitional section; and (2) the inclusion of meaningful descriptive content, offering more than a passing reference. Studies that mentioned the term without further elaboration were excluded to ensure conceptual depth and analytical rigour.  
The second subset consisted of 25 studies selected for architectural analysis. For this research, a metaverse architectural model is defined as a structured framework that outlines the components, layers, or mechanisms involved in the design, implementation, or operation of a metaverse system. Studies were included if they (1) proposed structured architectures, such as layered models, modular frameworks, or domain-specific system designs, and (2) described two or more functional components (e.g., infrastructure layer or virtual world). Moreover, models were not limited by application domain, as long as they were explicitly framed as metaverse architectures. Both subsets were analysed using the unified thematic framework developed in this study, allowing for a consistent conceptual interpretation across definitional and architectural perspectives.  
\begin{table}
\begin{tabular}{p{142.3 pt} p{142.3 pt}} \hline \hline
**Inclusion Criteria** & **Exclusion Criteria** \\ \hline Peer-reviewed journal and conference papers & Non-peer-reviewed publications (e.g., blogs, magazines) \\ \hline Published in English between 2013 and 2025 & Non-English publications \\ \hline Studies that propose or discuss definitions of the metaverse & Studies that mention the metaverse without defining or analysing it \\ \hline Studies that propose or analyse metaverse architecture models & Studies that do not include architectural or structural discussion \\ \hline Accessible full-text articles & Articles for which full text was not retrievable \\ \hline \hline \end{tabular}
\end{table}
Table 1: Inclusion and exclusion criteria.