OEP: 34 Title: Ontology Oracle Standard Author: zhangmh<siovanus@126.com> Type: Standard Status: Accepted Created: 2018-12-26
The OEP-34 Proposal is a standard interface for Ontology Oracle, this standard allows you to get outside world data via http request in smart contracts.
With the development of smart contract DApp, the requirement of using outside world data is more and more intense. For example, a flight insurance smart contract depends on if the flight delayed. But for blockchain, it's hard to get outside world data in smart contracts.
Ontology Oracle play a role as data carrier and can solve this problem. It makes it possible to obtain outside world data in smart contracts.
The OEP-34 proposal is the standard specify how the oracle works.
Simple oracle contract only have single admin operator account, which used to sign the data and transaction. You can also run several operators with same admin operator account to guarantee operator's availability.
Admin operator account is defined in simple oracle contract. Oracle fee will be sent to admin and only admin can set oracle outcome. Admin is responsible for the result it provide.
Simple oracle contract is easy to use for the organization who want to provide data service and want to deploy oracle contract.
Not all data service provider want to deploy an oracle contract. They can register their operator account and data method in some "oracle contract platform". Then listen to oracle request in oracle contract platform, obtain and serialize data, sign result and send it to oracle contract platform. Platform verify the signature and put result in contract storage. Oracle fee will be sent to the operator account whose method users invoke. Operator account is responsible for the result it provide.
Oracle contract platform is designed for someone who want to run a platform that operators can join and provide service without deploying oracle contract.
public static bool CreateOracleRequest(string request, byte[] address)request string of request body, defines how to get the data and how to serilize the data.
address the caller's address, will verify it's signature and pay oracle fee.
public static bool SetOracleOutcome(byte[] txHash, byte[] result)txHash the txHash of oracle request
result result of the oracle request
public static byte[] GetOracleOutcome(byte[] txHash)txHash the txHash of oracle request
public static bool RegisterOperator(string method, byte[] pubKey, byte[] address)method the method that the operator provide, users can use this method in request to get data via this operator
pubKey the public key of operator wallet
address the address of operator wallet
Notify(["createOracleRequest", request, address])Notify(["setOracleOutcome", txHash, status, errMessage])Oracle request must satisfy OEP-34 format so that operator can recognize, for example:
req = """{
"scheduler":{
"type": "runAfter",
"params": "2018-06-15 08:37:18"
},
"tasks":[
{
"type": "httpGet",
"params": {
"url": "https://data.nba.net/prod/v2/20181129/scoreboard.json"
}
},
{
"type": "jsonParse",
"params":
{
"data":
[
{
"type": "Array",
"path": ["games"],
"sub_type":
[
{
"type": "Struct",
"sub_type":
[
{
"type": "String",
"path": ["gameId"]
},
{
"type": "String",
"path": ["vTeam", "teamId"]
},
{
"type": "String",
"path": ["vTeam", "score"]
},
{
"type": "String",
"path": ["hTeam", "teamId"]
},
{
"type": "String",
"path": ["hTeam", "score"]
}
]
}
]
}
]
}
}
]
}"""
More oracle request examples see: README
OEP-34 Python Oracle Contract Template: Python Template
Operator listen request of oracle contact, fetch the data via http get/post method, and serialize the data via ontology neovm standard, then send signed result to oracle contract.
OEP-34 Golang Operator Template: Operator Template