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# System prepended metadata

title: RFC Meeting - UTXO - 2020-05-19

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# 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. 



