> For the complete documentation index, see [llms.txt](https://docs.rddl.io/rddl-network/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rddl.io/rddl-network/basics/proof-of-productivity/actor-selection.md).

# 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
sequenceDiagram
participant Validator
participant Challenger
participant Challengee
Participant Planetmint-Node

loop Availability Check - until 2 available actors are found
Validator ->> Validator: select challenger & challengee
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>
```