A Blockchain-based Semantic Exchange Framework for Web 3.0 toward Participatory Economy

Web 3.0 is now attracting the interest of researchers from academics and industries. It is considered to be the next generation of the Internet where participants can control their data, identities, and capabilities to make decentralized decisions and construct participatory economy. There are two mainstream developments of Web 3.0 as follows, including Blockchain Web 3.0 and Semantic Web 3.0. When the concept of Web 3.0 first emerged, it was identified as a semantic web, which can make Internet data machine-readable [1] and reduce energy consumption for processing and transmission. The current definition of Web 3.0 [2] was prevailing with the help of blockchain technologies, which can make participants get rid of tech giants and control user-generated content. Besides, since artificial intelligence and edge computing play important roles to connect Web 3.0 participants in a smart and lightweight way, they are also considered vital components of Web 3.0.

The diversified underlying technologies of Web 3.0 are similar to Web 2.0 mainly driven by cloud computing, social networks, and mobile connectivity. Instead of being controlled by tech giants, Web 3.0 allows all participants to make decisions to participate in constructing value networks, which should permit participants without the need of having the expertise of underlying technologies, like DeFi Money Legos [3]. Thus, Web 3.0 can be supported by multiple technologies like blockchain, artificial intelligence, edge computing, and semantic communication, which can easily coordinate to construct value networks to achieve participatory economy based on decentralized decision making among participants.

Although several new technologies are emerging as main components to construct value networks in Web 3.0, blockchain is considered the main technology for the participatory economy in many cases. Few researchers focus on how to integrate the components of new technologies into blockchain-based Web 3.0 toward the participatory economy. DeCAST [4] utilizes the integration of blockchain and federated learning to construct parallel intelligent transportation systems, which are effective and practical for smart mobility. A unified blockchain-semantic framework [5] is proposed to capture the benefits of blockchain, semantic extraction, and communication to improve interaction efficiency for Web 3.0. Besides, given the steps of the integration of new technologies in Web 3.0, it is necessary to consider how to make value circulated in the participatory economy to attract participants to join in Web 3.0 decision-making.

Blockchain, semantic extraction and communication can be utilized to reduce information overloaded, reduce energy consumption, and construct efficient interactions toward the participatory economy by extracting semantic information from raw data and implementing sharing in a decentralized manner. However, even capitalizing on the benefits of the above technologies, the design toward the participatory economy still faces many difficulties. On the one hand, it is difficult to quantify and transact semantic information circulated in Web 3.0. The reason is that producers and consumers are difficult to maximize their revenue and utility [6]. On the other hand, Web 3.0 is supported by a public blockchain platform, which makes pending semantic information exposed to both parties. Consumers can copy semantic information without payments to maximize their benefits [7] in current marketplaces.

In this paper, we attempt to complement the understanding of blockchain, semantic extraction and communication playing an important role in Web 3.0. We also develop a fair and efficient mechanism based on blockchain and semantic communication to tokenize semantic information and enable semantic exchange by utilizing the Non-Fungible Token (NFT), Stackelberg Game, and Zero Knowledge Proof (ZKP) toward participatory economy. Our contributions are summarized as follows.

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  We propose a new semantic exchange framework, that tokenize semantic information to facilitate semantic exchange by using blockchain.

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  In this framework, we formulate a Stackelberg game-based semantic trading mechanism to design optimal pricing strategies.

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  To facilitate fair and privacy-preserving transactions between producers and consumers, we utilize zero-knowledge proof to transact transformed semantic information without publishing authentic one before payments.

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  To show clearly the applications and mechanisms, we utilize urban planning to display how the above contributions work.

In this section, we describe the NFT-based semantic exchange scheme to facilitate semantic circulation. We also propose a Stackelberg game-based dynamic semantic trading mechanism to maximize the utility and revenue of semantic information. Moreover, we construct a zero-knowledge proof-based semantic sharing mechanism to enable fair authentic semantic sharing.

Urban planning activities are aided significantly by leveraging the proposed framework, which can incorporate the benefits of blockchain and semantic communication to construct Web 3.0 infrastructures. Semantic communication can reduce information overloaded to support real-time semantic interactions and minimize energy consumption for sustainable blockchain implementations. Blockchain can provide traceable semantic information status to enable semantic sharing in untrusted environments. Urban planning requires a tremendous amount of data from other counterparts to support interactions from different locations, as shown in Fig. 3. Producers can extract the contour from images of a certain category of construction, and the corresponding snapshots (semantic information) can be transmitted to respective consumers [11]. Instead of transmitting original images, the extracted contour can reflect key objects and the appearance of certain urban areas to reduce information overloaded. Once urban designers obtain the contour of certain areas from other designers, they can design a panoramic for urban planning.

However, information circulated in the urban planning activities can be duplicated easily, which makes that other urban planning designers are not willing to exchange it without any benefit and profit. For the same reason, it is unfair for producers to release semantic information first, which makes other urban planning designers can pay nothing to receive the core contour of certain areas. Moreover, since semantic information is valuable, it is necessary to construct a trading mechanism to guide semantic exchange in urban planning activities.

The proposed framework is based on the above two infrastructures to build fair and efficient semantic exchange mechanisms, as shown in Fig. 3. The designed zero-knowledge proof-based semantic sharing mechanism can implement fair and efficient transactions among urban designers by downsizing semantic information to exchange the contour of semantic information without releasing core designs first. It utilizes the NFT-based semantic exchange scheme to facilitate downsized semantic information produced from spatial data to circulation in urban planning activities. The proposed Stackelberg game-based semantic trading mechanism can facilitate urban planning activities constructing efficient trading marketplaces to facilitate the circulation of semantic information.

To evaluate the proposed framework and mechanisms, we implement the simulation case to illustrate the efficiency, as exhibited in Fig. 4. Fig. 4(a) shows the communication overhead among tradition communication (Tradition), blockchain-based semantic communication (Unified) [5], and our proposed mechanism (Ours). The blockchain module is supported by a practical byzantine fault tolerance algorithm with four nodes. The semantic module is implemented by Pytorch. The size of the transmitted messages among those mechanisms is 1 MB, 100 KB, and 1 KB, referring to Fig. 3. The amount of semantic information represents exchanged number of messages. The communication overhead is the time that semantic information is recorded in the blockchain module. As shown in Fig. 4(a), the proposed mechanism is more efficient than the compared mechanisms. Fig. 4(b) illustrates how the revenue of producers is affected by different parameters of the semantic trading mechanism as the number of iterations increases. With the increase of parameters, the costs take up more weight in the revenue function, which causes a decrease in the income of producers.

We overview recent open challenges in terms of blockchain, semantic communication, and Web 3.0, as shown in Table I. Then we also elaborate on several of them in the following.

Verification of Semantic Information: In scenarios that require high privacy and security, e.g., automotive industries, verification of semantic information is critical to perform operations correctly. It is impossible to publish semantic information on public Web 3.0 platforms, and leverage semantic information without any verification. Thus, zero-knowledge proof combined with pragmatic functions of semantic communication is expected to share private and authentic semantic information to protect privacy and security in Web 3.0. Besides, since proofs generated by ZKP can be verified given mathematical relationships, reputation mechanisms can be utilized to classify and exclude malicious Web 3.0 participants.

Price Bubbles of NFT-mapped Semantic Information: Although semantic information can be considered as NFT-based Web 3.0 assets circulating in the marketplaces, it is difficult to avoid price bubbles in current market mechanisms, like OpenSea [14]. The English Dutch auction mechanism [15] is promising to eliminate price bubbles in the circulation of semantic information.

Semantic Interoperability: Since Web 3.0 is integrated with blockchain and semantic communication, semantic interoperability not only includes semantic information circulated among multiple blockchains but also interacted with multiple semantic tasks. The former can be implemented by cross-chain technologies combined with verification, while the latter should consider how to extract the same characteristics between different types of semantic tasks.

Task-Oriented Layer 2 Solutions: Participants have to continuously exchange semantic information after perceiving environments to improve communication quality, which is time and resource-consuming. Current Layer 2 solutions may be a practical method to improve the performance of blockchain and semantic communication-based Web 3.0, which can provide off-chain interactions in a decentralized and traceable way.

In this paper, we present our understanding and research gaps in Web 3.0, Blockchain, and Semantic Communication. To this end, we propose a fair and efficient blockchain-based semantic exchange framework for the participatory economy. In this framework, we utilize NFT to circulate semantic information in the blockchain to construct value networks. After that, we consider optimal buying and pricing strategies for counterparts transacting with semantic information by a Stackelberg game approach. We also take fairness into account and leverage the zero-knowledge proof to enable authentic semantic sharing. A case study of urban planning and simulation results are implemented to illustrate the efficiency of the proposed framework. Finally, key challenges, opportunities, and future research related to blockchain and semantic communication for Web 3.0 are discussed.