IPVS/AS Using Triples as the Data Model for Blockchain Systems Dennis Przytarski Agenda • Motivation • Our approach • Evaluation • Example Dennis Przytarski • Using Triples as the Data Model for Blockchain Systems 2 Motivation Blockchain Systems • Initially designed for cryptocurrencies • Simple and fixed data model • Other scenarios • Automotive • Full history of a vehicle • Real Estate • Record of land titles • Voting • Reduce voter fraud Dennis Przytarski • Using Triples as the Data Model for Blockchain Systems 3 Motivation Blockchain Systems latest application state • Key-value data model World State • Simple query engine queries Query Key-value store • World state Engine (Document store) • Scenarios is derived from • Transportation/Trucking Blockchain • Tracking journey stops, parcel service Ledger Block n-2 Block n-1 Block n • Supply Chain Integrity Header Header Header • Food chain, waste management TRXN TRXN TRXN ... ... ... • Requirements • Flexible information model • Query engine for Transaction • World state Key Value • History (analytics, audit trails) key value ... ... based on [1] CAR0 {color:“blue“,make:“Ford“} Example Dennis Przytarski • Using Triples as the Data Model for Blockchain Systems 4 Merge Blockchain and Database Systems BLOCKCHAIN SYSTEMS DATABASE SYSTEMS • immutability • generic but flexible data model • tamper-resistance • powerful query engine DESIGN REQUIREMENTS • maintain a flexible information model and an efficient data representation • support a powerful query engine • preserve the integrity of the blockchain‘s data structure (tamper-resistance) Dennis Przytarski • Using Triples as the Data Model for Blockchain Systems 5 Data Model • Key-value • values are often serialized • if key is not known, a full scan is necessary • no powerful query engine, just get/set operations • Relational • too strict for immutable data • schemas evolve over time leading to schema changes • Triples • flexible schemas without maintaining an one-size-fits-all schema • triples are facts data of interest are easier to extract Dennis Przytarski • Using Triples as the Data Model for Blockchain Systems 6 Merkle B-Tree Hash A Root node … Pointer Hash B Pointer Hash C Pointer Hash D Node Data Data Data Hash B Hash C Hash D’ • Pointer: Memory address • Hash: Hash over the node’s data [2]: The Merkle B-Tree: Li, Feifei, et al. "Dynamic authenticated index structures for outsourced databases." SIGMOD 2006. Dennis Przytarski • Using Triples as the Data Model for Blockchain Systems 7 Architecture latest application state World State queries Query Query Key-value store Engine Engine (Document store) queries queries historical latest application application is derived from state state Blockchain Blockchain Ledger Block n-2 Block n-1 Block n Block n-2 Block n-1 Block n Header Header Header Header Header Header TRXN TRXN TRXN ... ... ... latest application state Transaction Merkle B-tree entity attribute value Key Value <Triple> key value CAR0 car/color blue CAR0 {color:“blue“,make:“Ford“} ... ... Example CAR0 car/make Ford ... Example Dennis Przytarski • Using Triples as the Data Model for Blockchain Systems 8 Advantage (1/2) Replace three data stores by one Blockchain Block n-3 Block n-2 Block n-1 Block n Header Header Header Header TRXN TRXN TRXN TRXN ... ... ... ... Storage Architecture Analytics Blockchain World State Blockchain Transaction log Graph database Key-value store on file system Triplestore Relational database is is (Document store) exported derived from from replaced by Ledger Dennis Przytarski • Using Triples as the Data Model for Blockchain Systems 9 Advantage (2/2) Built-in Data Integrity Checks (Tamper-resistance) • The database systems ‚Analytics‘ and ‚World State‘ are not aware of the blockchain‘s data structure data integrity checks must be done manually Query Query Query Engine Engine Engine if needed if needed built-in data data integrity data integrity integrity checks checks are checks are (tamper-resistance) done manually done manually Analytics Blockchain World State Blockchain Transaction log Graph database Key-value store on file system Triplestore Relational database is is (Document store) exported derived from from Ledger Dennis Przytarski • Using Triples as the Data Model for Blockchain Systems 10 Problem • High storage requirements • Optimization mechanisms ( efficient storage techniques) • data compression • data encoding • reuse of already stored data structures Dennis Przytarski • Using Triples as the Data Model for Blockchain Systems 11 Example Transaction 1 Transaction 2 <B9F, name, „Pluto“> <B9F, type, „dwarf_planet“> <B9F, type, „planet“> Block 1 Block 2 The query engine uses Hash FC8 Hash 2F7 1 4 the Merkle B-trees of a Node AEV AEV block to compute the A <= name A <= name result of a query Hash E87 Hash FAA Hash E87 Hash C29 Nodes are 2 3 2 5 stored in a <B9F, name, „Pluto“> <B9F, type, „planet“> <B9F, name, „Pluto“> <B9F, type, „dwarf_planet“> … … … … key-value store Key Value Root of identical node after FC8 1 first block Query Block 1 E87 2 SELECT ?type ASOF n FAA 3 WHERE Query result Root of 2F7 4 [?object name „Pluto“] for n=1: ?type is planet after second block [?object type ?type] for n=2: ?type is dwarf_planet Block 2 C29 5 Dennis Przytarski • Using Triples as the Data Model for Blockchain Systems 12 Contact Details Thank you! University of Stuttgart IPVS/AS Dennis Przytarski Email: [email protected] Dennis Przytarski • Using Triples as the Data Model for Blockchain Systems 13 References • [1]: Androulaki, Elli, et al. "Hyperledger fabric: a distributed operating system for permissioned blockchains." Proceedings of the Thirteenth EuroSys Conference. ACM, 2018. • [2]: Li, Feifei, et al. "Dynamic authenticated index structures for outsourced databases." Proceedings of the 2006 ACM SIGMOD international conference on Management of data. ACM, 2006. • Merkle, Ralph C. "A digital signature based on a conventional encryption function." Conference on the theory and application of cryptographic techniques. Springer, Berlin, Heidelberg, 1987. • C. Mohan, Tutorial: Blockchains and Databases (VLDB 2017) Dennis Przytarski • Using Triples as the Data Model for Blockchain Systems 14.