# Charting Past, Present, and Future Research in the Semantic Web and Interoperability
## 4 Results from Network Analysis
The following table (Table 6) summarizes the top twenty most frequently used keywords. As can be seen, \"SW\" (semantic web) is the most frequently occurring keyword, owing to its inclusion in the search query. The keyword \"ontology\" appears as the second most frequently used. As a result of this finding, designers, users, and domain experts must agree on shared and reusable conceptualizations and knowledge to comprehend the actual discourse in a particular domain. Additionally, the terms \"interoperability\" and \"SI\" (semantics interoperability) appear on the list, indicating that interoperability is a critical component of increasing the usability of distributed information systems, enabling structured search and data sharing and laying the groundwork for higher-level (web3) services and processing [71]. Similarly, semantic interoperability can be used to ensure the interoperability of IoT devices from various suppliers to reduce costs associated with data analysis and facilitate rapid decision making [72]. Figure 4: Co-authorship network. According to Gephi's citation analysis, the selected publications cited one another. According to both local and global citations, the top ten most cited publications are listed in Table 7. Among all publications, ref. [73] received the most citations. Two researchers, [PERSON] and [PERSON], listed in Table 5 as top contributors, also have publications in the Table 7 list. This finding is surprising, because the most prolific authors' influence is still limited compared to the authors listed in Table 7. As a result, no significant relationship exists between the number of publications and the total number of citations received. Surprisingly, two publications have extremely high global citation counts: [66] has 1189 citations and [74] has 703 citations, even though their local citation counts are relatively low. These two publications discuss the role of ontologies in the semantic web's architecture and their use in organizing registries and classifying all web services. These results demonstrate that these studies laid the groundwork for subsequent publications in the fields of interoperability and semantics. A closer examination of Table 7 reveals that [PERSON], [PERSON], and [PERSON] all have ontology, semantic technologies, knowledge management, and artificial intelligence backgrounds. This may account for their high global citation count. network. Then, we preprocessed and refined the keywords to ensure homogeneity, consistency, and accuracy. For example, full-length keywords such as semantic web, semantic interoperability, and the Internet of Things were abbreviated. In the visualization map, two keywords in close proximity are assumed to share a similar research topic or direction. To generate the keyword co-occurrence network, the data were loaded into VOSviewer, and the density-based spatial clustering using the full-counting method was employed [82; 83]. Additionally, the threshold of keyword occurrences was set at four. As a result, six clusters with different colors were obtained, as depicted in Figure 5. Each node in the figure corresponds to a keyword, and the node size reflects the co-occurrence frequency of the keyword. The density determines the distance between two nodes, and the higher this density, the shorter the distance between two keywords. The details regarding each cluster are presented in Table 8.  
From Figure 5, it is evident that the largest cluster is the red one. This cluster focuses on the fundamental building blocks of the semantic web, including ontologies and languages. The languages and technologies used for the construction of the semantic web provide valuable instruments for representing the semantics of profile data [84]. Ontologies and metadata languages play a significant role in integrating statical data on the web and annotating services [85]. In the semantic web context, several approaches are devoted to providing processable semantics expressed in meta-models, such as RDF, OWL, and OIL.