Crowdsourced repositories have become an increasingly important source of information for users and businesses in multiple domains. Everyday examples of tourism crowdsourcing platforms focusing on accommodation, food or travelling in general, influence consumer behaviour in modern societies. These repositories, due to their intrinsic openness, can strongly benefit from independent data quality modelling mechanisms. In this context, building trust & reputation models of contributors and storing crowdsourced data using distributed ledger technology allows not only to ascertain the quality of crowdsourced contributions, but also ensures the integrity of the built models. This paper presents a survey on distributed trust & reputation modelling using blockchain technology and, for the specific case of tourism crowdsourcing platforms, discusses the open research problems and identifies future lines of research.info:eu-repo/semantics/publishedVersio

Leal, Fátima

Malheiro, Benedita

Moreira, Fernando

Veloso, Bruno

English

Repositório Científico do Instituto Politécnico do Porto

ScienceDirectAvailable online at www.sciencedirect.comProcedia Computer Science 160 (2019) 457–4601877-0509 © 2019 The Authors. Published by Elsevier B.V.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)Peer-review under responsibility of the Conference Program Chairs.10.1016/j.procs.2019.11.06510.1016/j.procs.2019.11.065 1877-0509© 2019 The Authors. Published by Elsevier B.V.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)Peer-review under responsibility of the Conference Program Chairs.Available online at www.sciencedirect.comProcedia Computer Science 00 (2019) 000–000www.elsevier.com/locate/procediaThe 4th International workshop on Big Data and Networks Technologies(BDNT 2019)November 4-7, 2019, Coimbra, PortugalDistributed Trust & Reputation Models using BlockchainTechnologies for Tourism Crowdsourcing PlatformsBruno Velosoa,d, Fátima Lealb, Benedita Malheiroa,c,∗, Fernando Moreirad,e,faINESC TEC, Campus da Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, Porto, PortugalbCCC/NCI – Cloud Competency Centre, National College of Ireland, Mayor Street Lower, IFSC, Dublin, IrelandcISEP/IPP – School of Engineering, Polytechnic Institute of Porto, Rua Dr. António Bernardino de Almeida, 431, Porto, PortugaldUPT – Universidade Portucalense, Rua Dr. António Bernardino de Almeida, 541, Porto, PortugaleIJP, REMIT – Universidade PortucalensefIEETA – Universidade de Aveiro, Aveiro, Portugal.AbstractCrowdsourced repositories have become an increasingly important source of information for users and businesses in multiple do-mains. Everyday examples of tourism crowdsourcing platforms focusing on accommodation, food or travelling in general, influenceconsumer behaviour in modern societies. These repositories, due to their intrinsic openness, can strongly benefit from independentdata quality modelling mechanisms. In this context, building trust & reputation models of contributors and storing crowdsourceddata using distributed ledger technology allows not only to ascertain the quality of crowdsourced contributions, but also ensures theintegrity of the built models. This paper presents a survey on distributed trust & reputation modelling using blockchain technologyand, for the specific case of tourism crowdsourcing platforms, discusses the open research problems and identifies future lines ofresearch.c 2019 The uthors. Published by Elsevier . .is is ss rti l r t - - li s ( tt :// r tiveco ons.org/licenses/by-nc-nd/4.0/)i ility of the Conference Program Chairs.Keywords: Trust; Reputation; Data Integrity; Blockchain; Social Computing.1. IntroductionData crowdsourcing has become a major source of information in multiple domains. Everyday, examples of crowd-sourced data applications such as accommodation, food or media contents abound and, above all, have large influenceover consumer behaviour in modern societies. People chose hotels, restaurants, or movies based on the “wisdom of the∗ Corresponding author. Tel.: +351 22 83 40 500; fax: +351 22 83 21 159.E-mail address: mbm@isep.ipp.pt1877-0509 c© 2019 The Authors. Published by Elsevier B.V.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)Peer-review under responsibility of the Conference Program Chairs.Available online at www.sciencedirect.comProcedia Computer Science 00 (2019) 000–000www.elsevier.com/locate/procediaThe 4th International workshop on Big Data and Networks Technologies(BDNT 2019)November 4-7, 2019, Coimbra, PortugalDistributed Trust & Reputation Models using BlockchainTechnologies for Tourism Crowdsourcing PlatformsBruno Velosoa,d, Fátima Lealb, Benedita Malheiroa,c,∗, Fernando Moreirad,e,faINESC TEC, Campus da Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, Porto, PortugalbCCC/NCI – Cloud Competency Centre, National College of Ireland, Mayor Street Lower, IFSC, Dublin, IrelandcISEP/IPP – School of Engineering, Polytechnic Institute of Porto, Rua Dr. António Bernardino de Almeida, 431, Porto, PortugaldUPT – Universidade Portucalense, Rua Dr. António Bernardino de Almeida, 541, Porto, PortugaleIJP, REMIT – Universidade PortucalensefIEETA – Universidade de Aveiro, Aveiro, Portugal.AbstractCrowdsourced repositories have become an increasingly important source of information for users and businesses in multiple do-mains. Everyday examples of tourism crowdsourcing platforms focusing on accommodation, food or travelling in general, influenceconsumer behaviour in modern societies. These repositories, due to their intrinsic openness, can strongly benefit from independentdata quality modelling mechanisms. In this context, building trust & reputation models of contributors and storing crowdsourceddata using distributed ledger technology allows not only to ascertain the quality of crowdsourced contributions, but also ensures theintegrity of the built models. This paper presents a survey on distributed trust & reputation modelling using blockchain technologyand, for the specific case of tourism crowdsourcing platforms, discusses the open research problems and identifies future lines ofresearch.c© 2019 The Authors. Published by Elsevier B.V.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)Peer-review under responsibility of the Conference Program Chairs.Keywords: Trust; Reputation; Data Integrity; Blockchain; Social Computing.1. IntroductionData crowdsourcing has become a major source of information in multiple domains. Everyday, examples of crowd-sourced data applications such as accommodation, food or media contents abound and, above all, have large influenceover consumer behaviour in modern societies. People chose hotels, restaurants, or movies based on the “wisdom of the∗ Corresponding author. Tel.: +351 22 83 40 500; fax: +351 22 83 21 159.E-mail address: mbm@isep.ipp.pt1877-0509 c© 2019 The Authors. Published by Elsevier B.V.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)Peer-review under responsibility of the Conference Program Chairs.458 Bruno Veloso  et al. / Procedia Computer Science 160 (2019) 457–4602 B. Veloso, F. Leal, B. Malheiro and F. Moreira / Procedia Computer Science 00 (2019) 000–000crowd”. However, as the amount of data increases, so does the information overloading and the user ability to discernamong options and make rational choices. Typically, crowdsourcing platforms raise trustability questions since theyneither store user background data, nor adopt reliable technology, making recommendation particularly hard to relyon. Nowadays, false data in crowdsourcing platforms distort important social decisions related to politics, media, andlife in general. As such, trust & reputation modelling has arguably become a core research area in data science. It canbe used to establish the quality of the crowdsourced information and the trustworthiness of the contributors.To ensure data authenticity, i.e., avoid manipulation from unethical stakeholders, blockchain should be a key sup-port technology of any crowdsourcing platform. By uniquely associating contributors to contributions, blockchainensures data authenticity and traceability. It facilitates the process of recording transactions – on-line reviews, or-ders, payments, account tracking – and tracking assets in a network. The adoption of blockchain technology preventsagainst malicious behaviours and ensures the reliability of transactions. Developing crowdsourcing platforms withbuilt-in trust & reputation modelling supported by blockchain will arguably have a substantial impact to the quality ofthe information provided, e.g. travellers will be able to rely on the available reviews when booking hotel, readers willbe able trust news curated by other readers or e-costumers will be able to trust the reputation of a product, service orprovider.This paper surveys trust & reputation systems supported by blockchain technologies and, then, identifies the mainchallenges within tourism crowdsourcing platforms. The main goal is to compare existing models and detect futureresearch trends to ensure the quality and authenticity of tourism-related crowdsourced data.The rest of this article is structured as follows. In Section 2 we describe a systematic literature review on trust& reputation models using Blockchain technology. In Section 3, we identify the main challenges associated withthe distributed trust & reputation models. Finally, Section 4 details the research trends on blockchain-based trust &reputation models.2. Related WorkBlockchain is a distributed and decentralised public ledger, i.e., it is a sequence of blocks holding all transactionrecords, working as a conventional public ledger. This technology ensures that the transactions are: (i) encrypted; (ii)validated; (iii) stored by multiple entities; and (iv) immutable. It has been applied to a wide spectrum of applications,ranging from cryptocurrency, financial services, risk management, Internet of Things to social services [9]. Accordingto Pilkington [8], blockchain grants: (i) decentralised immutable and traceable reputation; (ii) unique users, i.e., onlyregistered users can contribute with ratings or reviews; and (iii) portable and transverse reputation. In addition, theanalysis of the reviews and the reviewers reputation can indicate the reputation of the service itself. Therefore, anhigher reputation indicates higher service quality, allowing, for example, the provider to increase the price [7].The application of blockchain to crowdsourcing platforms is relatively new. The five works found in the literature[2, 1, 3, 6, 5] were published since 2017. They include three works on trust [2, 6, 3] and two on reputation [1, 5].Regarding the blockchain technology used, four use Ethereum open source framework [1, 3, 6, 5] and one relies on aproprietary solution [2].• Buccafurri et al. [2] developed in 2017 a blockchain protocol called tweetchain to encode transactions and createmeshed replications for a twitter-based application.• Bhatia et al. [1] described in 2018 a reputation model for a crowdsourcing platform using the Ethereumblockchain. The crowdsourcing platform is a talent pool, where candidates can find jobs.• Lu et al. [6] presented in 2018 ZebraLancer, a freelancer service finder and service payment crowdsourcingplatform, which keeps transactions private and anonymous. This platform builds a trust model and implementsthe Ethereum blockchain technology.• Fernández-Caramés and Fraga-Lamas [3] reported in 2018 a decentralised blockchain framework for storingmedical health information. The blockchain Ethereum framework was applied to keep patient records privateand to model the trustworthiness of the medical staff.• Li et al. [5] proposed in 2018 a decentralised crowdsourcing job finding and posting platform. The authorsadopted the ethereum to build the distributed reputation model based on the past behaviour of each professional. Bruno Veloso  et al. / Procedia Computer Science 160 (2019) 457–460 459B. Veloso, F. Leal, B. Malheiro and F. Moreira / Procedia Computer Science 00 (2019) 000–000 3Table 1 presents the comparison of the crowdsourcing platforms in terms of trust & reputation model used,blockchain technology adopted and domain of application.Table 1. Crowdsourcing platforms that adopts blockchain technologyContribution Model Blockchain Technology DomainBuccafurri et al. [2] Trust Tweetchain TwitterBhatia et al. [1] Reputation Ethereum Job FindingLu et al. [6] Trust Ethereum Payment SystemFernández-Caramés and Fraga-Lamas [3] Trust Ethereum HealthLi et al. [5] Reputation Ethereum Job FindingThis literature survey shows that there are few crowdsourcing platforms concerned with ensuring the quality andauthenticity of the crowdsourced data. In particular, in the tourism domain, where crowdsourcing is extremely popular,no such mechanisms are found in the prevailing platforms. For this reason, the following sections will specificallyaddress the case of tourism crowdsourcing platforms.3. Main ChallengesTourism is an enriching activity which fosters relaxation and well-being. Not only personal intellectual satisfactiontends to increase with enriching travelling experiences, but the tourism industry promotes the economical developmentof countries. Therefore, the exploitation of the trustworthiness and authenticity of tourism data is relevant both to indi-viduals and society. In this context, integrative, scalable approaches to trust & reputation modelling can take advantageof blockchain technology, overcoming the vulnerability of traditional computational approaches. This scenario raisesmultiple research questions:1. How does false information affect tourism crowdsourced platforms?2. How to ensure the trustworthiness of the tourism crowdsourced information?3. Which are the most suitable processing methods to support decentralised modelling algorithms?4. Does blockchain-based trust & reputation modelling improve the reliability of tourism crowdsourced platforms?On-line trust & reputation are built over time based on quality and amount of contributions. While trust definesthe reliability of users and resources based on direct experience, reputation is based on third party experiences, e.g.,the crowd [4]. According to Önder et al. [7], the modelling of the reputation of contributors defines the quality of theservice itself, which can be used for pricing purposes. However, since the overwhelming majority of crowdsourcingplatforms does not ensure the authenticity of the volunteered data, trust & reputation models can suffer from maliciouscontributions. To explore the above problems this study proposes using blockchain together with trust & reputationmodelling.4. Research ProposalThe proposed methodology for tourism crowdsourcing platforms integrates the blockchain technology with trust &reputation modelling. By incorporating the blockchain principles, the transactions become encrypted, validated, storedby multiple entities and immutable. The trust & reputation modelling grants quality assessment of the reviews andreviewers and, ultimately, of services. To process, exploit and discover trends in crowdsourced data, such platformsneed:• Data collection: Collect and store the crowdsourced data in the blockchain.• Data processing: Build trust & reputation models and explore big data techniques, including data stream pro-cessing techniques, using a scalable cloud computing environment.• Data analysis: Perform multiple-criteria analysis to identify patterns and trends in user behaviour.460 Bruno Veloso  et al. / Procedia Computer Science 160 (2019) 457–4604 B. Veloso, F. Leal, B. Malheiro and F. Moreira / Procedia Computer Science 00 (2019) 000–000• Validation: Use predictive accuracy metrics, such as Root Mean Square Error (RMSE) and Mean AbsoluteError (MAE), and classification metrics like Precision, Recall and F-Measure to determine the quality of rec-ommendations and, consequently, of the trust & reputation models.By ensuring the authenticity of the shared information, building trust & reputation models of contributors and main-taining a traceable history regarding all crowdsourced contributions, the current research proposal aims to enrich thetraveller experience by providing reliable information. This steams from the fact that the personal recommendationsissued by these platforms depend on the quality and authenticity of the crowdsourced data.References[1] Bhatia, G.K., Kumaraguru, P., Dubey, A., Buduru, A.B., Kaulgud, V., 2018. WorkerRep: building trust on crowdsourcing platform usingblockchain. Ph.D. thesis. IIIT-Delhi.[2] Buccafurri, F., Lax, G., Nicolazzo, S., Nocera, A., 2017. Tweetchain: An alternative to blockchain for crowd-based applications, in: Interna-tional Conference on Web Engineering, Springer. pp. 386–393.[3] Fernández-Caramés, T.M., Fraga-Lamas, P., 2018. Design of a fog computing, blockchain and iot-based continuous glucose monitoring systemfor crowdsourcing mhealth, in: Multidisciplinary Digital Publishing Institute Proceedings, p. 37.[4] Leal, F., Malheiro, B., Burguillo, J.C., 2018. Trust and reputation modelling for tourism recommendations supported by crowdsourcing, in:Rocha, Á., Adeli, H., Reis, L.P., Costanzo, S. (Eds.), Trends and Advances in Information Systems and Technologies, Springer InternationalPublishing, Cham. pp. 829–838.[5] Li, M., Weng, J., Yang, A., Lu, W., Zhang, Y., Hou, L., Liu, J.N., Xiang, Y., Deng, R.H., 2018. Crowdbc: A blockchain-based decentralizedframework for crowdsourcing. IEEE Transactions on Parallel and Distributed Systems 30, 1251–1266.[6] Lu, Y., Tang, Q., Wang, G., 2018. Zebralancer: Private and anonymous crowdsourcing system atop open blockchain, in: 2018 IEEE 38thInternational Conference on Distributed Computing Systems (ICDCS), IEEE. pp. 853–865.[7] Önder, I., Treiblmaier, H., et al., 2018. Blockchain and tourism: Three research propositions. Annals of Tourism Research 72, 180–182.[8] Pilkington, M., 2016. 11 blockchain technology: principles and applications. Research handbook on digital transformations 225.[9] Zheng, Z., Xie, S., Dai, H.N., Chen, X., Wang, H., 2018. Blockchain challenges and opportunities: a survey. International Journal of Web andGrid Services 14, 352–375.

Distributed Trust & Reputation Models using Blockchain Technologies for Tourism Crowdsourcing Platforms

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Distributed Trust & Reputation Models using Blockchain Technologies for Tourism Crowdsourcing Platforms

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