Optimistic Input submission

[paluh]

One of the limitations of the current execution flow of Marlowe contracts on chain is its inability to easily handle different orderings of Inputs which permutations (like deposits) preserve the same semantics. We solve this usually by introducing permutations to the contract itself and relying on the merkleization (this works fine but moves parts of the Contract handling offchain - users have to provide their own safe storage beside the ledger).
This is a bit speculative but it seems that without singnificant changes to the main validator (we should allow noop tx) we should be able to implement optimistic Input submission which can be reclaimed at any point or used at appropriate time during contract execution. The idea can be possibly implemented by using approach similar to validatorToken which was described here:

https://github.com/input-output-hk/MIPs/pull/1/files#r931122201

and its "stepper" extension which was shortly discussed here:

https://github.com/input-output-hk/MIPs/pull/1/files#r932891000

In principle "optimistic Inputs" could be handled through (possibly additional) "enhanced" minting policy script which optionally allows this and dedicated small spending validator for UTxO carrying this future Input which allows application at an appropriate time (if valid) or reclaim of the Input. Of course I'm not entirely sure how hard it is gonna be to implement.

Do you find this idea interesting? Do we want to explore this area of design space?

[paluh]

Of course this approach can open up a can of worms like - possible "transaction size lock" attack. We should probably restrict this approach significantly and the policy should be parameterized by the restriction.
I'm tempted to close this thread now...