Trustworthy Semantic Web Knowledge Management + E-Business + Semantic Web = Semantic E-Business
Tutorial: Blockchain Technologies and the Semantic Web Blockchain meets Semantic Web … ·...
Transcript of Tutorial: Blockchain Technologies and the Semantic Web Blockchain meets Semantic Web … ·...
Tutorial: Blockchain Technologies and the Semantic Web
Blockchain meets Semantic WebLuis-Daniel Ibáñez – University of [email protected]
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebGoals – Review and Discuss
› Semantic Web for Blockchains– How Semantic Web could help Blockchains?
› Blockchains for Semantic Web– How Blockchains could help Semantic Web?
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebAgenda (Approximate)
› Semantic Web for Blockchains– Knowledge Representation (15m)– Interoperability (15m)– Discussion (10m)
› Blockchains for Semantic Web– Trust & Proof layers (15min)– Data Marketplaces and incentives (15min)– Discussion (10min)
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Distributed Systems
Cryptography
Game Theory
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebA Blockchain Ecosystem
Community (Users and/or miners)
Consensus protocol intransaction order and validity
Incentive
Blockchain (Database)
SemWeb for Blockchains
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebKnowledge Representation
› Blockchains started as very low level artefacts
› But now have several layers of information
› How to represent them and their contents?
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
J. Pfeffer - Eth0n and Beyond – Keynote to International Workshop on Linked Data and Distributed Ledgers 2017
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
J. Pfeffer - Eth0n and Beyond – Keynote to International Workshop on Linked Data and Distributed Ledgers 2017
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● On statements about blockchains● On statements asserted inside blockchains
– Proof and Trust. We’ll see that later
Reasoning possibilities!
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● Provide the right level of abstraction● Represent concepts that vary from blockchain to
blockchain– Consensus algorithm used– “Transaction”– Participant versus validator/miner
Challenges
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
H. Ugarte. A more pragmatic Web 3.0 – Linked Blockchain Data
● Aimed at describing Bitcoin and Ethereum● Account, Block, Transaction, Payload
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● Ethereum specific
eth0n
https://ethon.consensys.net/
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
P. Tasca & C. Tessone Ontology of Blockchain Technologies, principles of Identification and Classificationhttps://dx.doi.org/10.2139/ssrn.2977811
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
http://www.untitled-inc.com/the-token-classification-framework-a-multi-dimensional-tool-for-understanding-and-classifying-crypto-tokens/
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebBlockchain Interoperability
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebBlockchain Interoperability
● Heterogeneity of– Data (Like in Linked Data)– Communities (Like in content production networks) – Protocols– Incentives
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebOne chain to rule them all...
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebNot happening...
● Throughput limits● Variety of use cases
– Miners or participants, privacy and cryptography requirements
● Natural competition● Fear of becoming centralized again
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebWhat happens though is...
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Data Silos
Blockhain Silos
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebQuestions...
● How to use RDF et al. as a mean for data interoperability for Blockchains?
● How to enable interoperation at transaction level?
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebData Interoperability
● One half: Lifting blockchains● Other half: Put RDF inside blockchains
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebAdding data in Blockchains (1)
● Many Blockchains are space constrained– Most of them were not designed for this
● How to add data directly on them?
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebAdding data in Blockchains (1)
Attaching Semantic Metadata to Cryptocurrency Transactions. Ibáñez et al. DeSemWeb 2017
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebComparison of compression approaches
Attaching Semantic Metadata to Cryptocurrency Transactions. Ibáñez et al. DeSemWeb 2017
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebAdding data in Blockchains (2)
● Hashing-out– Store a hash in the Blockchain, document somewhere else– Document can be verified against the hash.
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebAdding data in Blockchains (2)
hash#x9567hh31335
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebAdding data in Blockchains (2)
hash#x9567hh31335
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● Substitute location-based addressing for content-based addressing.
● S/Kademlia DHT + Git + BitTorrent
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
https://medium.com/textileio/whats-really-happening-when-you-add-a-file-to-ipfs-ae3b8b5e4b0f
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Reconstruct document via Link Traversal
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● If not enough nodes hosting, no content● Incentives needed (more on that later)
Tradeoff
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebTransaction interoperability
Blockchain ABlockchain B
Transact asset
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebBlockchain Interoperability (BI)
Smart Contract@ Blockchain A
Smart Contract@ Blockchain B
Mutual call that preserves properties on both sides
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebBlockchain Interoperability (BI)
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebCosmos
› “TCP for Blockchains”
› Zones are regular blockchains
› A Hub that uses a consensus protocol to connect them
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebPolka Dot
› Parachains, similar to hubs but market-controlled
› Special protocol to handle inter-consensus
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebCrosses the SemWeb boundary, but...
● Have we ever thought on transactions in Linked Data at web scale?
● What consistency guarantees beyond Eventual Consistency?
● LD-Scripts and services executing all over the place?
● This type of constructions could be used for “adding consistency to the Web”
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Some open problems
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● Highlight Blockchains that are compatible/incompatible
● Explain possible property loss when plugging to other blockchains
Reasoning on Blockchain descriptions
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● Given a collection of interdependent Smart Contracts and a set of Blockchain ecosystems, where to deploy each piece?
● Similar to Multi-Cloud deployment
Deployment of Smart Contracts
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● A Blockchain ecosystem may die● Or become too expensive● How to migrate to another ecosystem?
Migration of Blockchains
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● Who decides on changes in the protocol● Two hackers in Zug sipping Chai Latte?● A Foundation incorporated in Singapore?● The community? How?
Governance
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● Do you see any other problems?
Discussion
Blockchains for SemWeb
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● Trust & Proof– Those layers of the Semantic Web cake…– We will see applications to Semantic Log Auditing and Scholar
Publication
● Incentives for publishing and maintaining data– Subsidies don’t scale
Problems of Semantic Web
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
“The Logic layer enables the writing of rules while the Proof layer executes the rules and evaluates together with the Trust layer mechanism for applications whether to trust the given proof or not.”
Trust & Proof
https://www.w3.org/2001/12/semweb-fin/w3csw
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebTrust and proof
Example applications
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Semantic Audit Logs
Use L2TAP ontology
Sutton & Samavi. Blockchain Enabled Privacy Audit Logs. ISWC 2017
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Semantic Audit Logs
How to protect against collusion to tampering?
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebExperimental Evaluation
Bottomline: Linear in the size of the log
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Preserving Government Decisions
● Use case for Greek government decisions● Problem 1: They are not machine readable nor
easily verifiable– That is solved with Linked Data
● Problem 2: No one trust them, fear that decisions may be overruled unlawfully– Blockchains kick in
Beris & Koubarakis. Modeling and Preserving Greek Government Decisions using Semantic Web Technologies and Permissionless Blockchains. ESWC 2018
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Preserving Government Decisions
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Enabled provable checks
● A timestamp proves that a message existed prior to some point in time; is a “proof-of-existence”
● Input: a decision– It was stamped on date dt– Does not match anything stamped
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Decentralised Scholarly Communication● Scientific publishing is centralised
– Many researchers dislike that
● Decentralised models have been proposed– Authors self-publish articles– Articles are semantic entities (SPAR ontologies)– (Open) Reviews are also self-published and linked to articles
● Problem– We killed the monster… but we can be monsters too...
Hoffman et al. Smart Papers – Dynamic Publications on the Blockchain. ESWC 2018
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Collapse of Trust (1)
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Collapse of Trust (2)
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Collapse of Trust (3)
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Collapse of Trust (3)
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Approach – Papers as Smart Contract● A paper is a Ethereum Smart Contract● Functions for all paper interactions
– Publish– AddReview
● Statements about papers and their links are stored as transactions in Ethereum
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Evaluation● Time to commit
– Few minutes.
● Cost– Fluctuates according to Ethereum market– 2$ per call (when measured, nowadays is less)
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Pattern for applications● Shift trust from a central entity to trust in a
Blockchain ecosystem [Protocol + Participants + Incentives + Crypto-primitives]
● Evaluate cost and risks– Public blockchains have more participants, but you have to pay in
cryptocurrency– Private blockchains require participants to put the resources to run
the protocol
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
P. Evans-Greenwood. Blockchains and Linked Data. Keynote to Workshop on Linked Data and Distributed Ledgers @ WWW2017
Pathways to trust
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Paid in Cryptocurrency Paid in your hardware running the protocol
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Some open problems
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
General RDF verification● Hands-on session!
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
What do we want when querying?● SELECT ?s ?o
WHERE { ?s ex:pred ?x SERVICE <A_Blockchain>{ ?x ex:other_pred ?s}
}● SELECT ?s ?o
WHERE { ?s ex:pred ?x . { ?x ex:other_pred ?s} IS VERIFIED
} (Output explains who verifies and where)
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Smart Contracts as Web Services● With very special properties (and costs) ● True or False?
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Discussion● Any further problems● Questions?
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Incentives for a data economy
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebIn contrast to the traditional web where
advertisement fueled a lot of the growth. This raises the question how the WoD can
● (i) maintain its success when government subsidies disappear and
● (ii) convince commercial entities to share their wealth of data
T. Grubenmann et al. Decentralizing the Semantic Web: Who will pay to realize it? DeSemWeb 2017
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Storage Query Pricing Exchange
Steps of selling data
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● Decentralising these steps● Adding trust/proof to these steps● Powering incentive mechanisms through
cryptocurrencies
Blockchains can help...
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● If not enough nodes hosting, no content● Incentives needed (more on that later)
Tradeoff
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● If not enough nodes hosting, no content● Incentives needed (more on that now)
FileCoin
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● A decentralized storage network that is auditable, publicly verifiable and designed on incentives.
● Clients pay a network of miners for data storage and retrieval; miners offer disk space and bandwidth in exchange of payments.
● Miners receive their payments only if the network can audit that their service was correctly provided.
FileCoin
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● An interactive proof system in which a prover defends a publicly verifiable claim that it is dedicating unique resources to storing one or more retrievable replicas of a data file
Proofs of replication
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● How to query a Web of Data stored in this?– Does querying like on P2P works?– Link Traversal?
● There are alternatives in the market (Sia,Storj)– Follow links across systems?
Querying is ongoing work
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● Given a query on a database, put a price on it● It’s a hard problem
– If you want it arbitrage-free is very hard– Or you can leave everyone set their own price, but that has other
implications
Pricing
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
WebOcean Protocol
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
● Privacy (Multi-Party Computation Revival)● Data Protection
– Immutability vs right to be forgotten
● Sell processing without a middle man● Use a Smart Contract to deliver
– What should go on the Blockchain and what should not?
Some open problems
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web
Take-aways
● SemWeb technologies are already been used for interoperability by practitioners.– Let’s keep pushing that
● Blockchains provide decentralised “Trust & Proof” machinery– Trust the protocol/ecosystem/incentive in provide proof of something– An opportunity to re-decentralise the Web.
Blo
ckch
ain
Tech
nolo
gie
s and t
he S
em
an
tic
Web