# RFC Meeting - UTXO - 2020-05-19

https://github.com/iotaledger/protocol-rfcs/pull/11

## Participants

- Thibault Martinez
- Gal Rogozinski
- Luca Moser
- Wolfgang Welz
- Hans Moog
- Angelo
(- Maximilian Hase)

## Goals
- Review the RFC PR;
- Agree/disagree on its content;
- Make progress towards merging it;

## Discussion topics
- Output detailed design should contain the structure
- Redefine output ID

### Steps to change this RFC
- Detailed questions will be added as comments to the RFC
- Evolve into a detailed Chrysalis RFC: Details should be added on how this is implemented with IOTA specific details (this might require separate RFCs and discussions if it proves to be too complex):
- Reattachments
- Snapshots
- Solidification, what does solid mean in this context and so on.
- Does this change the TX layout?
- This UTXO specification assumes that we have Chrysalis
- Atomic transactions, for this spec we only need to UTXO necessary fields defined.
- White flag
- Unresolved questions: Concepts like below max depth and how this applies or doesn't apply.
- Remove the branching details unresolved question and anything that only ties to Coordicide.
- Opcode can be left in as motivation and we can reserve byte(s) for it
- Coloured coins specification should be a separate RFC.

### Drawback discussion
- A UTXO-based ledger is much more complex in the implementation than just a dictionary of balances.
- A UTXO-based ledger stores more information and therefore requires "potentially" more disk space.

### Unresolved questions
- We need to think about good unlock opcodes and options.
- Hardcode the sigcheck opcode for now.
- We need to define use cases for this and then decide what we can support and that can be at the same time supported by the Tangle (not slowing it down).
- We should define a PR that specifies the "branch based ledger state" as this is very closely related to the use of UTXO.
- This is Coordicide only.