An application's in-app prices for purchases should be listed in fiat currency as the price of cryptocurrencies often fluctuates greatly. Users will want to refer to this as a basepoint but also wish to use cryptocurrencies. To refer to accurate data on the price of the cryptocurrencies, an oracle is needed. They provide accurate information from a decentralized world (off-chain) to the blockchain world. There are a few potential oracle networks that may be used in the OPEN API, Chainlink, Oraclize, and GNOSIS. Speed and security will be the driving factors behind selecting an oracle.
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Thanks for the update dev! I'll check this out in the white paper.