To allow for inter-organisational processes in networks withlow trust, Supply Chains and corresponding information are moving tothe blockchain. On the blockchain, this information poses a scalabilitychallenge. To tackle this challenge, we propose a solution that minimisesthe data stored on the blockchain, which we base on semantic datamodelling in knowledge graphs, decentralised management of interlinkeddata, and a light-weight Smart Contract. In this demo, we focus onthe web agent to participate in Supply Chain networks built using ourapproach, and our corresponding data modellin

Braun, C. H.-J.

Käfer, T.

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A SoLiD App to Participate in a ScalableSemantic Supply Chain Network on theBlockchain (Demo)Christoph H.-J. Braun and Tobias KäferInstitute AIFB, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germanyuvdsl@student.kit.edu, tobias.kaefer@kit.eduAbstract. To allow for inter-organisational processes in networks withlow trust, Supply Chains and corresponding information are moving tothe blockchain. On the blockchain, this information poses a scalabilitychallenge. To tackle this challenge, we propose a solution that minimisesthe data stored on the blockchain, which we base on semantic datamodelling in knowledge graphs, decentralised management of interlinkeddata, and a light-weight Smart Contract. In this demo, we focus onthe web agent to participate in Supply Chain networks built using ourapproach, and our corresponding data modelling.Video http://people.aifb.kit.edu/co1683/2020/iswc-demo-chain/#v1 IntroductionBlockchain-based solutions make their way into business networks with limitedtrust, for instance into inter-organisational logistics networks: Examples includeIBM and Maersk’s TradeLens1 project or Deutsche Telekom/T-Systems andDatev’s Bizzbloxx2 project. While those solutions are gaining maturity, the scala-bility challenges of such solutions become apparent [3]: The inherent replication ofdata on the blockchain mandates that only the minimum amount of informationrequired for fulfilling the use-case should get stored on the blockchain.Therefore, we proposed a solution to store information off-chain and verify theinformation behind a supply chain using Linked Data and Smart Contracts [2].The off-chained data is described in RDF, and accessible in a RESTful manner(i. e. Linked Data). Only hashes, URIs, and links are stored on the blockchain.The hashes, URIs, and links allow for verification of the off-chain data usinga link-traversal-based querying approach and the Smart Contract, which weCopyright c© 2020 for this paper by its authors. Use permitted under CreativeCommons License Attribution 4.0 International (CC BY 4.0).1 https://techcrunch.com/2018/08/09/ibm-teams-with-maersk-on-new-blockchain-shipping-solution/2 https://www.datev.de/web/de/m/presse/pressemeldungen/meldungen-2019/geschwindigkeit-und-sicherheit-im-e-commerce-mit-bizzbloxx/presented in a previous demo at the 15th International Conference on SemanticSystems (SEMANTiCS) [1].For the presentation for the international/virtual audience of ISWC, we wantto focus on the information used around our previously presented approach, i. e.the data modelling of especially the participants’ profiles and their interaction.As a showcase, we present a user agent, which consumes said RESTful APIs andimplements said data modelling to manage the exchange and verification of dataand the interaction among the users. Our contributions of this paper are:– An architecture based on the practices around the decentralised social networkSoLiD3, which is based on RESTful communication, data modelling in RDF,and Linked Data Notifications as ontology and protocol to describe andinteract with notifications4. We tie the social network to the interlinkedhistory of a product using the standardised Activity Streams vocabulary5.– An app that is centred around a supply chain network participant’s profileURI. The app allows for participation in the supply chain network, managesthe notifications, and verifies the data using the blockchainThis paper is structured as follows: We first distinguish our current work fromour previous work and provide a short overview of other related research(§ 2).In order to help the understanding of the later sections, we then cover ourexample use-case most briefly (§ 3). We next present our architecture and thedata modelling (§ 4). Last, we conclude (§ 5).2 Related ResearchThe previous version presented at SEMANTiCS was a command-line interfacewritten in Java, which did not make use of the practices around SoLiD such asLinked Data Notifications, Activity Streams, and HTML5/JavaScript-based UIs.For the overall solution, we specifically:– defined an ontology to describe the interlinked history of a product on theblockchain based on the ontologies OntoPedigree [6] and EthOn6– connect this product history to the participating users’ profiles– make thus described data available as Linked Data– hash the product data using the RDF hashing algorithm of [4]– store hashes, URIs, and links in a Smart Contract on the Ethereum blockchainThe term “user profile” used in the previous version refers mainly to the Ethereumaddress identifying the corresponding user. In the previous version, the exchangeof information and interaction among users was assumed to be managed off-chain without further specification. In contrast, the presented version specifies3 http://solid.mit.edu/4 http://www.w3.org/TR/ldn5 https://www.w3.org/TR/activitystreams-vocabulary/6 https://ethon.consensys.net/the participants’ profiles and their interaction among each other using RDFmaking it therefore possible to visualize or automate off-chain data exchangeand verification. Based around the principles of the decentralised social networkSoLiD, the current version’s modelling extends the previous work regardingoff-chain semantic data modelling and management.Other previous works in the intersection of blockchain and BPM have beenperformed by the BPM community7 like the seminal work around Caterpillar [5],which typically contain solutions that potentially put a comparatively high loadon the blockchain, both regarding computation and storage, as they put theprocess logic and/or storage onto the blockchain, whereas our solution usesthe blockchain only for verification and linking. For data management off-chainin the context of blockchain systems, distributed hash tables (DHTs) like theInter-Planetary File System (IPFS)8 are often used. Our solution however buildson Linked Data, i. e. web servers and RDF. In contrast to DHTs, web servers canimplement requirements such as data sovereignty and access control in a straight-forward fashion. [7] also stores data off-chain with verification capabilities, butdoes so at the decision of a blockchain trigger and in a place at the decisionof this trigger, and not by default in a place at the decision of the user. Theirapproach is also built on chain code generation for pre-defined process models,whereas our approach does not build on process models and our Smart Contractcode does not change.3 Example Use-caseOur example is a supply chain network that is centred around the perishablegood of a fish. The fish is caught by a fisher, transported by a trucker, and soldat a corner shop. Using our solution, we aim to allow for transparency along thissupply chain by documenting the corresponding hand-overs. [2] and the videoaccompanying this paper contain a longer form of the example.4 System and Data ArchitectureWe first describe the data pods of each network participant, before we discuss theSmart Contract and the app. The overall architecture can be found in Figure 1.Data Pods We base our architecture on the idea of SoLiD data pods3, wherethe person that owns the data pods is identified using a URI, and describedusing the FOAF vocabulary9. Following the Linked Data Notifications W3Crecommendation4, these URIs have an inbox to send requests to. Theseinboxes follow the Linked Data Platform10 W3C recommendation. In our7 https://www.slideshare.net/IngoWeber2/blockchain-and-bpm-reflections-on-four-years-of-research-and-applications8 https://ipfs.io/9 http://xmlns.com/foaf/spec/10 http://www.w3.org/TR/ldpFig. 1. The architecture of our demo. Each participant in the network has its ownSoLiD pod accessed using the app. Optionally, the participants also participate with anode in the Ethereum blockchain network.case, goods on the supply chain can be sent as offers, as defined by theActivity Stream vocabulary5 W3C recommendation. These offers are linkedto the product pedigree, and a description of how the information can bevalidated using the blockchain. We show a depiction of the data modelling inFigure 2.Smart Contract Our Smart Contract for Ethereum stores (a) pairs of RDFgraph hashes of product pedigree and URIs where the hashed data can befound, and (b) links to the previous pair. More details can be found in [2].App The app takes as input the URI of the person. Then it follows hyperlinksto acquire all the required RDF data of interest for the person participatingin the supply chain: The offered goods, their blockchain-based validationinformation, and whether the transferred good can be approved. The webagent allows a user to participate in the network and follow the hand-overand approval protocol of [2], and the verification. The web agent is built onVue.js with RDF processing from N3.js, and interaction with Ethereum usingweb3.js. The agent uses the hashing algorithm of [4] in the form of an APIthat wraps its implementation in Java.5 ConclusionWe presented a SoLiD app to participate in a supply chain network, where data isstored decentrally in Linked Data and verification is possible using a blockchain.The app allows for accessing the decentrally stored data using link-traversalbased querying of RDF, documents the hand-overs contained in the supply chainin semantic data and on the blockchain and does the verification.Using the app, we want to showcase the participation in blockchain-basedsolutions by the example of a supply chain, while addressing scalability anddata sovereignty problems of blockchain technology with off-chain semantic datamodelling.foaf:Personxsd:stringfoaf:namewd:Q12737077(Occupation)wdt:P106(occupation)ldp:Containerldp:inboxas:Offerldp:containsas:targetfoaf:Personas:actorrdfs:Resourceas:objectp:Pedigreerdfs:seeAlsoFig. 2. The data modelling in our demo. UML classes and associations depict RDFSclasses and our specialisations of RDFS domain and range respectively. The dashedpart refers to the ontology that we described in detail in [2]. The URI prefixes canbe looked up at http://prefix.cc/, besides ethOn:, which is short for http://ethon.consensys.net/, and p:, which is short for http://purl.org/pedigree#.References1. Braun, C.H.-J., and Käfer, T.: Verifying the Integrity of Hyperlinked InformationUsing Linked Data and Smart Contracts. In: Proc. 15th SEMANTiCS (2019)2. Braun, C.H.-J., and Käfer, T.: Verifying the Integrity of Information along a SupplyChain using Linked Data and Smart Contracts. In: Proc. Posters and Demos at the15th SEMANTiCS (2019)3. Eberhardt, J., and Tai, S.: On or Off the Blockchain? Insights on Off-ChainingComputation and Data. In: Proc. 6th ESOCC (2017)4. Hogan, A.: Skolemising Blank Nodes while Preserving Isomorphism. In: Proc. 24thWWW (2015)5. López-Pintado, O., Garcıa-Bañuelos, L., Dumas, M., Weber, I., and Ponomarev,A.: Caterpillar: A business process execution engine on the Ethereum blockchain.Journal of Software Practice and Experience 49(7) (2019)6. Solanki, M., and Brewster, C.: Consuming Linked data in Supply Chains: Enablingdata visibility via Linked Pedigrees. In: Proc. 4th COLD WS @ 12th ISWC (2013)7. Weber, I., Xu, X., Riveret, R., Governatori, G., Ponomarev, A., and Mendling, J.:Untrusted Business Process Monitoring and Execution Using Blockchain. In: Proc.14th BPM (2016)

A SoLiD app to participate in a scalable semantic supply chain network on the blockchain (Demo)

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A SoLiD app to participate in a scalable semantic supply chain network on the blockchain (Demo)

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