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Listen to Software Engineering Daily: https://softwareengineeringdaily.com/2021/04/07/chainlink-connecting-smart-contracts-to-external-data-with-sergey-nazarov/TranscriptJM: Tell me a little bit more about the data sources for Chainlink. Like how do thosedata sources get vetted and how does the data make its way onto the chain?SN: Right, absolutely. So there're actually two approaches here and I think they'reboth important and the flexibility of how you acquire data is important. The first approach is thatyou have an oracle network and that oracle network is a collection of nodes that are incentivizedjust like blockchain miners and Bitcoin miners are incentivized. Those nodes are incentivized togo out and get accurate data in order to generate the most accurate, highly reliable resultpossible. In the first version of how data is put into a smart contract, this oracle network of anywhere fromseven to over 30 nodes basically goes to an API at a data provider that is considered a highquality data provider. Often that's determined by users. So users will say, “Hey, we want that data provider.” Chainlink also has a reputation system where we track how well each node, and even more and more now how each data provider is performing. And so better data providersget to continue selling their data to Chainlink networks, whereas worst data providers are kind ofnot as used by node operators because they're either not responsive or not returning the rightresults. And so there's actually a reputation system baked into Chainlink, and it's quitefascinating because the system inherently puts all of the data on chain and generates a lot ofproof about what's going on with the oracles.In any case, in the first variant of the system you can go to any data provider, you can go toreally any API in the world and you can request from it and you can come to consensus on thedata from that source assuming you can get other sources or you can come to some model ofconsensus that the user wants around that data. And that doesn't require the data provider to doanything, right? So the benefit of this system is that you have a layer of consensus and youhave a lot of proof that the data was acquired from a data provider and the data providers don'tneed to change anything about their infrastructure, right? So the data providers just continue toprovide their APIs, operate the way they have always operated and just do what they'resupposed to be doing. This is the system through which a good amount of the data is acquiredand then the data providers are more than happy to sell their data to Chainlink nodes becauseit's consumed into these applications which they're all excited about.The second version is when a data provider runs their own Chainlink node. And what thatbasically means is the data provider gets a lightweight signing appliance. They basically get alightweight signing application that allows them to connect their APIs internally to their ownofficial node. And then that node publishes a contract on-chain, and that on-chain contract is arepresentation of that data provider. So now there's an on-chain contract that's therepresentation of that data providers services. And that on-chain contract gets requests fromother smart contracts for data to be given to them because, once again, a blockchain cannottalk to an API. A blockchain has to have an oracle to speak with any API in the outside realworld. And so the second variant is where data providers that are more interested in kind of sellingtheir data to the blockchain ecosystem or more convinced about that, and we have many dataproviders already doing this live. We have data for sports events, weather events, marketevents, all kinds of things out in the real-world already live on production with data providersrunning their own production nodes. This variant allows you to get data essentially directly froman official node run by a data provider. It has the benefits of getting data directly from a dataprovider running their own node. It has the limitation in that the data provider now has to be ableto make sure that they are properly connected, that their APIs stay up according to the node andall these other kinds of nuances. The benefit that they get is they are connected to manydifferent chains all at once. And in reality this variant basically requires the data provider to wantto opt-in to some kind of infrastructure. It requires them to want to say that, “Hey, I want to kindof run a function in the cloud or I want to run some kind of node myself and I want to make atechnical investment in that.”What we found so far is that the majority of data providers just want to sell their data tosomebody and they want to provide that to an oracle network that just retrieves their data andsells that data successfully to a smart contract. There are some data providers that want to runtheir own node and we're working with a lot of those, but I think that's something that's going toevolve more slowly.[00:16:33] JM: You mentioned this reputation system for how data gets verified as quality. Howdoes that reputation system work? How do you vet and ensure quality data?[00:16:45] SN: So once again there's two levels. There's one level of the node operators andassuring that they're operating properly and then there's the level of the data providersresponding properly. In terms of the node operators, the way that the Chainlink system works isthat node operators are committing to certain service level commitments, right? They'rebasically, in many cases, on-chain committing to a certain degree of service. And they'recommitting to that because the on-chain activity that they do is immediately public to everybodyas soon as it happens. So I think the big nuance difference between a reputation system in the web world and areputation system in the blockchain world is that data is immediately available publicly. It isimmediately available for people to know that a node did not respond for a certain period oftime. And that lack of response is recorded on-chain immutably for everybody to analyze. Andwe actually have multiple ecosystem teams. We have multiple kind of block explorer-like thingsand marketplaces that are all able to analyze the same data about both node operators anddata providers.So basically the way that it looks is that the node operators are expected to perform to a certaindegree on-chain. Those expectations are clear. They are then able to perform, or in some casesif they're not able to perform, they are not able to stay on that oracle network. And then the dataproviders themselves, for the ones that run their own nodes, it becomes pretty clear what theirresponses, are and if their responses are often wrong, then you know once again that dataprovider and their node might not be used in an aggregation. They might not be applied to thataggregation.In the cases where a node operator gets data from a data source, a lot of that data is actuallymore internal to the oracle network and that data is something that's in the process of gettingpublished on chain. So there is a certain amount of insight that node operators have about theresponsiveness of different data providers and different data sources. At this point the reputationsystem extends to node operators and to the node operators that are data sources. It willcontinue and is already being extended to cover data provi...