Beyond Price Feeds: Expanding the Definition of Oracles

Traditionally, when we think about oracles, we associate them with price feed oracles that provide off-chain data to on-chain smart contracts. But there's more to oracles than that. There are actually two main types:

• Input Oracle: delivers off-chain data to an on-chain context (like Chainlink Price Feeds)
• Output Oracle: delivers on-chain data to an off-chain context for advanced computation (such as The Graph Protocol or Hyper Oracle's zkIndexing)
• There's also a specialized third type called I/O oracle that combines both input and output oracles for enhanced functionality.

This post on the ETH Research goes into more detail on this topic and how to secure oracles with ZKPs instead of staking: https://ethresear.ch/t/defining-zkoracle-for-ethereum/15131