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Aggor

This document provides technical documentation for Chronicle Protocol's Aggor oracle system.

Table of Contents

Design Goals

  • Liveness, ie Aggor should whenever possible provide a price
  • Resilient, ie Aggor is adaptable and capable of handling multiple failure scenarios
  • Neutral, ie Aggor does not depend on a single oracle provider

Terminology

  • An Oracle is defined as a push-based oracle system, eg Chronicle Protocol, Chainlink, etc.
  • A TWAP is an onchain time-weighted average based oracle via which an asset's price can be derived without offchain components.
  • An oracle (lower case) is a generic term that can refer to both a TWAP or an Oracle.
  • The agreement distance is a mutable configuration defining the threshold until which Oracle values are defined as being in agreement.

Workflow

Note that Aggor's price derivation is generic and not bounded to its current specific implementation.

Setup

  1. User defines the set of Oracles to use in Aggor
    • Note that at least 2 different Oracles MUST be set
  2. User defines the TWAP to use in Aggor
  3. User defines the agreement distance
    • Note that this value SHOULD be derived via historical analysis of the configured Oracle providers
  4. User defines the age threshold
    • Note that this value SHOULD be derived based on the Oracle provider's update frequency

Price Derivation

The following price derivation takes place during any of Aggor's read functions:

values := [read(oracle) for oracle in oracles]
values := filter(\v -> is_valid(v) and is_not_stale(v), values)

if len(values) >= 3:
    return median(values)  # Path: 1

if len(values) == 2:
    if in_agreement_distance(values):
        return median(values)  # Path: 2
    else:
        twap_value := read(twap)
        if is_valid(twap_value):
            return median(values ++ twap_value)  # Path: 3
        else:
            # Error: No value derivation possible
            return 0  # Path 6

if len(values) == 1:
    return values[0]  # Path: 4

if len(values) == 0:
    twap_value := read(twap)
    if is_valid(twap_value):
        return twap_value  # Path: 5
    else:
        # Error: No value derivation possible
        return 0  # Path: 6