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Overview and definitions
- An oracle is an entity on the blockchain and lives in the oracle state tree in a full node.
- An oracle is operated by an oracle operator.
- The oracle operator creates an oracle through posting a oracle register transaction on the chain.
- The oracle register transaction register an account as an oracle. (One account - one oracle)
- Any user can query an oracle by posting an oracle query transaction on the chain.
- The oracle query transaction creates an oracle query object in the oracle state tree.
- The oracle operator scans the transactions on the blockchain for the
oracle query transaction through whatever means. Probably on the operator's own node.
- The oracle operator responds to the oracle query by posting an oracle response transaction on the chain.
- The oracle response transaction modifies the oracle query object by adding the response.
- After the response have been added, the oracle query object is closed, and is now immutable.
Technical aspects of Oracle operations
Oracles have a published API
- The API defines the format that queries should have. (query_format)
- The API defines the format answers will have. (response_format)
- The API defines the VM version under which the formats should be interpreted.
- If the VM version is 0 (?AEVM_NO_VM):
- the query and response formats are uninterpreted strings (byte arrays).
- the queries and responses are treated as strings when called from sophia contracts.
- For VM version corresponding to sophia:
- the query and response formats must be type representations, encoded according to the ABI.
- the queries and responses are interpreted as the types in the format specifications
Oracle responses have a type declaration
- Types should correspond to types in the smart contract language.
- There should be incentives to use simple types in oracle answers (boolean, integer).
- For example, through access cost in smart contracts.
Should oracle responses have restrictions on use?
- For example, should only the creator of the query be able to use the
answer in a smart contract?
- Should the framework support encryption/decryption of answers?
An oracle query/response has a TTL
- The actual response will remain on the chain.
- The response will be pruned from the state tree after a certain number of blocks.
- The cost of posting the answer should reflect the TTL.