> ## Documentation Index
> Fetch the complete documentation index at: https://docs.pragma.build/llms.txt
> Use this file to discover all available pages before exploring further.

# Optimistic Oracle

> Asserts and verifies real-world state

<Warning>
  This service is deprecated and is no longer available.
  If you need are building a prediction market or anything that requires an optimistic oracle,
  let us know and we can help you set up a custom solution.
</Warning>

<Info>
  This feature is currently under development. Content may be incomplete or subject to change.
</Info>

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.

### Optimistic Oracle

You can find Pragma's first implementation of the Optimistic Oracle on Starknet [here](https://github.com/astraly-labs/Optimistic-Oracle/tree/main), following [UMA](https://docs.uma.xyz/protocol-overview/how-does-umas-oracle-work)'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:

| Network          | Address                                                           | Explorer                                                                                                                                                                                                                                               |
| ---------------- | ----------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| Starknet Sepolia | 0x44ac84b04789b0a2afcdd2eb914f0f9b767a77a95a019ebaadc28d6cacbaeeb | [Starkscan](https://sepolia.starkscan.co/contract/0x44ac84b04789b0a2afcdd2eb914f0f9b767a77a95a019ebaadc28d6cacbaeeb) [Voyager](https://sepolia.voyager.online/contract/0x44ac84b04789b0a2afcdd2eb914f0f9b767a77a95a019ebaadc28d6cacbaeeb#accountCalls) |

### General Process

<Steps>
  <Step title="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
  </Step>

  <Step title="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
  </Step>

  <Step title="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
  </Step>
</Steps>