# Actor Selection

The CometBFT consensus algorithm selects the acting validator. The algorithm selects Block creators for each epoch/block.

The thereby elected validator is the master of ceremony for this very execution of the PoP and performs the following actions

1. selects a challenger and a challengee
2. verifies their availability via m2m (mqtt)
3. notarizes the selection via an InitPoP message containing
   * the validator-address,
   * challenger address
   * challengee address
   * block height
4. sends a PopInit command containing the block height of the PoP to the challenger and the challengee with the expectation that both will perform the PoP.

{% @mermaid/diagram content="sequenceDiagram
participant Validator
participant Challenger
participant Challengee
Participant Planetmint-Node

loop Availability Check - until 2 available actors are found
Validator ->> Validator: select challenger & challenge
Validator ->> Challenger: M2M: are you available?
Challenger ->> Validator: M2M: yes/no/no-answer
Validator ->> Challengee: M2M: are you available?
Challengee ->> Validator: M2M: yes/no/no-answer
end
Validator ->> Planetmint-Node: notarize InitPoP: validator, challenger, and challengee, block height
Validator ->> Challenger: M2M-Message PoPInit <block height>
Validator ->> Challengee: M2M-Message PoPInit <block height>" %}