Blockchains a new platform for semantically enabled transactions public
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Keynote at the SALAD Workshop at ESWC 2016. Gives an overview of blockchains and some thoughts on the link to the Semantic Web, Linked Data and Semantic Web Services
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Blockchains a new platform for semantically enabled transactions public
- 1. Blockchains: a New Platform for Semantically Enabled Transactions Prof. John Domingue Director, Knowledge Media Institute, the Open University, UK President STI International http://kmi.open.ac.uk/
- 2. Caveat • Semantic Web • Semantic Web Services • Blockchains
- 3. MOTIVATION
- 4. Our Position in the SW World
- 6. WEB IS A PLATFORM E-commerce Search Engine Social Web Portal Travel Online Services Cloud computing $28.83 $15.84 $12.29 $10.56 $17.93 $74.98 $107 $9.22 $6.77 $8.59 $6.3 $6.67 $5.37 $4.97 $3.63 $2.99 $3.1 $1.5 $1.40 $0.9 $2.22
- 7. Blockchain <-> SWS Relationship (1/2) • Blockchains implement trust • New (transaction) platform
- 8. Blockchain <-> SWS Relationship (2/2) • Simple concept with complex implementation • Re-use important • Identification important • No inbuilt search • Interoperates with plethora of systems • Implements legal, financial and asset based transactions
- 17. What is a blockchain? A blockchain is a permissionless distributed database, based on the bitcoin protocol that maintains a continuously growing list of transactional data records hardened against tampering and revision, even by operators of the data store's nodes. The initial and most widely known application of the blockchain technology is the public ledger of transactions for bitcoin and the inspiration of similar distributed ledgers known as altchains. Each blockchain record is enforced cryptographically and hosted on machines working as a data store Source: Wikipedia
- 19. Blockchain is a Linked List (1/2) A blockchain can be thought of as a linked list of transactions that is built with hash pointers instead of pointers Source: Bitcoin and Cryptocurrency Technologies - Arvind Narayanan, Joseph Bonneau, Edward Felten, Andrew Miller, Steven Goldfeder
- 20. Blockchain is a Linked List (2/2) A blockchain actually contains two different hash structures. The first is a hash chain of blocks that links the different blocks to one another. The second is internal to each block and is a Merkle Tree of transactions within the blocks. This allows for efficiently verifiable proofs that a transaction was included in a block.
- 22. Ethereum is a cryptocurrency platform and Turing-complete programming framework intended to allow a network of peers to administer their own stateful user-created smart contracts in the absence of central authority. It features a blockchain-based virtual machine that securely records and incentivizes the validation of transactions, i.e. code executions, made through a cryptocurrency called ether. Ethereum takes the primary developments used by BitTorrent and Bitcoin, the peer to peer network and the blockchain, and generalizes them in order to allow developers to use these technologies for any purpose. Source: Wikipedia Ethereum Blockchain Platform
- 23. Ethereum Blockchain Platform Ethereum is a 100% open source software platform to build distributed, decentralized applications Ethereum is 100% peer to peer, censorship-proof and corruption-proof. Ethereum can be used to build anything: Asset issuance, crowdfunding, domain registration, title registration,predictionmarkets, internet of things, voting, educational certificate issuing systems, hundreds of applications Source: Ethereum slides - Stephan Tual and Ethereum in 40 minites by Vitalik Buterin
- 24. Ethereum Virtual Machine Sources: Ethereum Development Tutorial The Ethereum Virtual Machine can be thought of as a large decentralized computer containing millions of objects, called "accounts", which have the ability to maintain an internal database, execute code and talk to each other. There are 2 types of Accounts: Externally owned account (EOA): an account controlled by a private key that has the ability to send ether and messages from it. ‘Smart’ Contract: an account that has its own code, and is controlled by code. Any user can trigger an action by sending a transaction from an EOA, setting Ethereum's wheels in motion. If the destination of the transaction is another EOA, then the transaction may transfer some ether but otherwise does nothing However, if the destination is a ‘Smart’ Contract, then the contract in turn activates, and automatically runs its code.
- 25. What are Ethereum Contracts? ‘Smart’ contracts are computer protocols that facilitate, verify, or enforce the negotiation or performance of a contract. ‘Smart’ contracts can be partially or fully self-executing, self-enforcing, or both. Smart contracts in Ethereum have the ability to read/write to their own internal storage, read the storage of the received message, and send messages to other contracts, triggering their execution in turn Sources: Wikipedia and Ethereum Development Tutorial and Ethereum - Introduction to Smart Contracts
- 26. Contracts in Ethereum Maintain a data store representing something which is useful to either other contracts or to the outside world Serve as a sort of externally owned account with a more complicated access policy Manage an ongoing contract or relationship between multiple users Provide functions to other contracts; essentially serving as a software library. Contracts in Ethereum generally serve 4 purposes: source: Richard Gendal Brown “A Simple Model for Smart Contracts” http://gendal.me/2015/02/10/a-simple-model-for-smart-contracts/
- 27. DApps Source: Ethereum - Stephan Tual A Đapp is a decentralised application which serves some specific purpose to its users, but which has the important property that the application itself does not depend on any specific party existing. Rather than serving as a front-end for selling or providing a specific party's services, a Đapp is a tool for people and organizations on different sides of an interaction use to come together without any centralized intermediary. A Dapp consists of two parts: a frontend, written in HTML or QML, and a backend (think of it as the ‘database’ for your frontend).
- 29. Characteristics of Blockchain DApps • Shared database • Multiple writers • Absence of trust • Disintermediation • Transaction interaction • Set rules • Validators • Asset backing http://www.multichain.com/blog/2015/11/avoiding-pointless-blockchain-project/
- 34. Course Contract Functions: Storage: enrol unenrol getStudents studentsPaid[address=0.6, address=0…. ] students [address, address, address] Course Administration ViewStudent View Enrol for 6 ETH! your Ethereum address password to private key Signing this transaction will transfer 6 ETH + gas from your account. Estimated gas cost is 0.02 ETH. Maximum gas cost is set to 0.05 ETH Enrol Student Enrolment Page Signed TX Unenrol Student Admin Ethereum address Admin password to private key Signing this transaction will transfer 6 ETH + gas from course admin account. Estimated gas cost is 0.02 ETH. Maximum gas cost is set to 0.05 ETH Unenrol Course Admin Page Signed TX Student List (Listing students is a free transaction) Course Enrolment Page Signed TX Student Address Array unenrolStudent Account 11 Student Account 23 Student Account 45 Student Account 67 Student Account 89 unenrol unenrol unenrol unenrol Student Account 67 Course Smart Contract
- 40. Services -> Smart Contracts Web service Operation 1 Operation 2 Operation N input input input output output output . ..
- 41. Services -> Smart Contracts Web service Operation 1 Operation 2 Operation N input input input output output output . ..
- 42. Services -> Smart Contracts Web service Operation 1 Operation 2 Operation N . ..
- 43. Services -> Smart Contracts Web service Operation 1 Operation 2 Operation N . ..
- 44. Services -> Smart Contracts Web service Operation 1 Operation 2 Operation N . ..
- 45. Services -> Smart Contracts Smart Contract . .. Transaction 1 Transaction 2 Transaction N
- 46. Services -> Smart Contracts Distributed Autonomous Organisation . .. Transaction 1 Transaction 2 Transaction N
- 47. • From • To • Value • Gas • Gas Price • Data • Nonce web3.eth.sendTransaction(transactionObject[, callback]) Transaction Creation Object
- 48. • Block Hash • Block Number • Transaction Hash • Transaction Index • From • To • Cumulative Gas Used • Gas Used • Contract Address • Logs Transaction Receipt Object web3.eth.getTransactionReceipt(hashString [, callback])
- 53. Transaction • From • To • Input – Value – Data • Cost – Currency – Price • Block information • Contract • Condition – Financial condition – Non financial condition • Effect – Financial effect – Non financial effect • History
- 54. Smart Contract • Transactions • Condition – Financial condition – Non financial condition • Effect – Financial effect – Non financial effect
- 55. SUMMARY
- 57. Summary (1/2) • Blockchain attracting a lot of commercial and community interest – Trusted mediator for legal and financial transactions – IoT platform – Disaggregation and disintermediation – Leaderless Distributed Autonomous Organisations
- 58. Summary (2/2) • Small subset of the SW/LoD community focused on processes/services/APIs • Lot to offer – Identification – Search – Re-use – Interoperability – Automation • Machine <-> machine communication in a human populated world
- 59. Acknowledgements • KMi@OU Implementation Team – Michelle Bachler – Kevin Quick • Discussants – Sören Auer, Fraunhofer – Adi Ben-Ari, Applied Blockchain – Carla Casilli, Mozilla Open Badges – Marc Eisenstadt, OU – Matthew English, Fraunhofer – Denis Gillet, EPFL – Hugh Halford-Thompson, Blockchain Tech Ltd – William Knottenbelt, Imperial College – Konstantin Kudryavtsev, Ethcore – Gary McKay, APII – Rebecca Migirov, Consensys – Titi Roman, Sintef – Philipp Schmidt, MIT Media Lab – Mike Sharples, OU – Elena Simperl, University of Southampton – Ashley Taylor, Consensys – Sergej Zerr, University of Southampton • Graphics – Harriett Cornish, OU