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An optimistic oracle is a decentralized mechanism in blockchain and Web3 systems that enables rapid inclusion of off-chain data or computation results on-chain without immediate verification. It operates on the principle of “optimistic” trust, assuming submitted data is correct unless challenged within a specified timeframe. If unchallenged, the data is considered valid; if disputed, it undergoes a verification process. This approach significantly reduces the latency and cost associated with bringing external information on-chain, as it only requires full verification in cases of disagreement. Optimistic oracles are particularly useful for complex computations, large datasets, or frequently updated information, enabling more efficient and scalable blockchain applications while maintaining a high degree of trust and security.

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Optimistic Oracle

You can find Pragma’s first implementation of the Optimistic Oracle on Starknet here, following UMA’s general interface. Our Optimistic Oracle works by making a truth claim about the world, stating that something has happened or is true. Once asserted, the assertion enters a challenge period during which someone can dispute it. If no one disputes it during the challenge window, the statement is taken as true. In case of a dispute, the data verification mechanism intervenes. The first iteration of the optimistic oracle is deployed on the following addresses:
NetworkAddressExplorer
Starknet Sepolia0x44ac84b04789b0a2afcdd2eb914f0f9b767a77a95a019ebaadc28d6cacbaeebStarkscan Voyager

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General Process

1

Assertion Submission

An Asserter submits a bonded assertion about a real-world state. The assertion must include:
  • Identifier: The specific price identifier being asserted
  • Timestamp: When the asserted fact occurred
  • Claim: Additional contextual information about the assertion
  • Currency: The ERC20 token used for rewards and fees (must be DVM-approved)
  • Bond: The stake amount backing the assertion’s accuracy
2

Dispute Window

During this phase:
  • A predefined “liveness period” begins
  • Disputers can challenge the assertion during this time
  • Disputers may use their own off-chain price feeds and methodologies to verify the assertion
  • The assertion remains in this state until either disputed or the window closes
3

Resolution

The assertion can be resolved in one of two ways:If Disputed:
  • The assertion is forwarded to the Data Verification Mechanism
  • Arbitration process begins
  • Final outcome is determined through verification
If Undisputed:
  • The assertion automatically becomes valid
  • Completion occurs after liveness period ends
  • The asserted state is accepted as truth