Within the “Bus” tree, each leaf is a commitment to:
- 1.Either an “asset” UTXO representing a number of zAssets (or zNFTs) (essentially an “IOU” for the corresponding underlying collateral locked on the Panther Vault); or
- 2.a “zAccount” UTXO, a record that keeps information about the owner of a zAccount.
The name ”'Bus Tree'' comes from UTXOs getting on the tree in batches of up to 64 UTXOs at once, rather than individually. To get on the “bus”, a UTXO needs to be put on a queue and wait until a miner (known as “Bus operator”) processes it and the other UTXOs on the queue.
The “bus” approach makes the process cost-efficient as all UTXOs in a queue share processing costs. As such, the individual cost for a transaction per user is much lower. On the other hand, users become dependent on the “Bus operator” who decides which queue to process and when to process it. Just like users of a blockchain incentivize miners to pick up their transactions by defining how much they are willing to pay for “gas”, Panther Protocol users define the reward (denominated in $ZKP) that they are willing to pay to the miner who processes their UTXOs.