Add ERC: Common Quote Oracle

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ERCS/erc-7726.md

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+---
+eip: 7726
+title: Common Quote Oracle
+description: Interface for data feeds providing the relative value of assets.
+author: alcueca (@alcueca), ruvaag (@ruvaag), totomanov (@totomanov), r0ohafza (@r0ohafza)
+discussions-to: https://ethereum-magicians.org/t/erc-7726-common-quote-oracle/20351
+status: Draft
+type: Standards Track
+category: ERC
+created: 2024-06-20
+requires: 7528
+---
+
+## Abstract
+
+The following allows for the implementation of a standard API for data feeds providing the relative value of
+assets, forcing compliant contracts to use explicit token amounts instead of price factors. This approach has been
+shown to lead to better security and time-to-market outcomes.
+
+## Motivation
+
+The information required to value assets is scattered over a number of major and minor sources, each one with their own
+integration API and security considerations. Many protocols over the years have implemented oracle adapter layers for
+their own use to abstract this complexity away from their core implementations, leading to much duplicated effort.
+
+This specification provides a standard API aimed to serve the majority of use cases. Preference is given to ease of
+integration and serving the needs of product teams with less knowledge, requirements and resources.
+
+## Specification
+The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 and RFC 8174.
+### Definitions
+
+- base asset: The asset that the user needs to know the value for (e.g: USDC as in "I need to know the value of 1e6 USDC
+  in ETH terms").
+- quote asset: The asset in which the user needs to value the `base` (e.g: ETH as in "I need to know the value of 1e6
+  USDC in ETH terms").
+- value: An amount of `base` in `quote` terms (e.g. The `value` of 1000e6 USDC in ETH terms is 283,969,794,427,307,000
+  ETH, and the `value` of 1000e18 ETH in USDC terms is 3,521,501,299,000 USDC). Note that this is an asset amount, and
+  not a decimal factor.
+
+### Methods
+
+#### `getQuote`
+
+Returns the value of `baseAmount` of `base` in `quote` terms.
+
+MUST round down towards 0.
+
+MUST revert with `OracleUnsupportedPair` if not capable to provide data for the specified `base` and `quote` pair.
+
+MUST revert with `OracleUntrustedData` if not capable to provide data within a degree of confidence publicly specified.
+
+MUST revert if the value of `baseAmount` of `base` in `quote` terms would overflow in a uint256.
+
+```yaml
+- name: getQuote
+  type: function
+  stateMutability: view
+
+  inputs:
+    - name: baseAmount
+      type: uint256
+    - name: base
+      type: address
+    - name: quote
+      type: address
+
+  outputs:
+    - name: quoteAmount
+      type: uint256
+```
+
+### Special Addresses
+
+Some assets under the scope of this specification don't have an address, such as ETH, BTC and national currencies.
+
+For ETH, the address will be `0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE` as per [ERC-7528](./eip-7528.md).
+
+For BTC, the address will be `0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB`.
+
+For assets without an address, but with an ISO 4217 <!-- TODO: Bug Sam about editing EIP-1 to allow certain ISO external links --> code, the code will be used (e.g. `address(840)` for USD).
+
+### Errors
+
+#### OracleUnsupportedPair
+
+```yaml
+- name: OracleUnsupportedPair
+  type: error
+
+  inputs:
+    - name: base
+      type: address
+    - name: quote
+      type: address
+```
+
+#### OracleUntrustedData
+
+```yaml
+- name: OracleUntrustedData
+  type: error
+
+  inputs:
+    - name: base
+      type: address
+    - name: quote
+      type: address
+```
+
+## Rationale
+
+The use of `getQuote` doesn't require the consumer to be aware of any decimal partitions that might have been defined
+for the `base` or `quote` and should be preferred in most data processing cases.
+
+The spec doesn't include a `getPrice` function because it is rarely needed on-chain, and it would be a decimal number of
+difficult representation. The popular option for representing prices can be implemented for [ERC-20](./eip-20.md) with decimals as
+`oracle.getQuote(base, quote, 10\*\*base.decimals()) and will give the value of a whole unit of base in quote terms.
+
+## Backwards Compatibility
+
+Most existing data feeds related to the relative value of pairs of assets should be representable using this standard.
+
+## Security Considerations
+
+This specification purposefully provides no methods for data consumers to assess the validity of the data they receive.
+It is expected of individual implementations using this specification to decide and publish the quality of the data that
+they provide, including the conditions in which they will stop providing it.
+
+Consumers should review these guarantees and use them to decide whether to integrate or not with a data provider.
+
+## Copyright
+
+Copyright and related rights waived via [CC0](../LICENSE.md).