## 4 Semantic Web  
The semantic web is a vision for the future of the web in which information is organized in a way that is more meaningful and machine-readable. It involves the use of metadata, ontologies, and linked data to enable computers to understand the content and context of web resources. Web 3.0 seeks to provide users with more control over their data and online interactions, as well as enabling seamless and secure transactions between parties. One of the key challenges facing the development of Web 3.0 is the need for intelligent and efficient handling of the vast amounts of data that will be generated by decentralized applications. This is where the semantic web comes in, as it provides a framework for organizing and processing data in a way that is more efficient and meaningful. The semantic web is implemented programmatically using a set of standards and technologies that enable machines to understand and process the meaning of data on the web. Some of the key technologies and standards used in the semantic web include the following:  
* RDF (Resource Description Framework) is a data model that provides a standard way to describe resources on the web. It defines a set of concepts and relationships for representing metadata about resources. * OWL (Web Ontology Language) is a formal language for representing and sharing ontologies on the web. An ontology is a set of concepts and relationships that define a domain of knowledge. * SPARQL (SPARQL Protocol and RDF Query Language) is a query language for RDF data. It allows users to retrieve and manipulate data stored in RDF format. * Linked Data are a set of best practices for publishing and interlinking data on the web. It enables data to be shared and reused across different applications and domains. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Corda** & **Ethereum** \\ \hline Network Type & Permissioned & Permissionless \\ Consensus Mechanism & Pluggable (e.g., BFT, Raft, Notary Services) & Proof of Work (PoW), transitioning to PoS \\ Language Support & Java, Kotlin & Solidity (Ethereum-specific language) \\ Privacy & Native support for privacy & Public by default, limited privacy features \\  & and confidentiality & Account-based model (balances \\ Transaction Model & Unspent Transaction Output (UTXO) model & and transactions) \\ Scalability & Focus on scalability and performance & Scalability challenges (e.g., network congestion) \\ Interoperability & Native support for interoperability & Interoperability through standards and protocols \\ Smart Contract Features & Flexible contract design and governance & Rich ecosystem of smart contract functionalities \\ Integration & Suitable for enterprise integration & Suitable for public and open applications \\ Development Tools & Corda Development Kit (CDK), Corda Node & Truffle Suite, Remix IDE, Web3.js, libraries \\  & API & Web3j (Java library for Ethereum interaction), \\ Language Libraries & N/A & ethereumj (Java implementation of Ethereum client), web3j (Java bindings for Ethereum JSON-RPC API) \\ \hline \hline \end{tabular}
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Table 1: Corda and Ethereum feature overview. While there are several technologies that enable Java applications to implement the semantic web, including Sesame and OWL API, arguably the most popular and well supported is Jena. An Apache project, Apache Jena is an open-source Java framework for building semantic web and linked data applications. It provides a set of tools for RDF and SPARQL standards, as well as for building and managing ontologies [10]. Apache Jena exposes several APIs and tools for working with RDF data. The core concept of the RDF model is represented by the Model interface. A model is a collection of RDF statements, where each statement consists of a subject, a predicate, and an object. The model can be seen as a graph structure, where nodes represent resources or literals, and edges represent relationships between them.