How to make sure every party agrees to protocol

Noumena Protocol Language
1

Hi - I’ve been playing around with the IOU starter example. Let’s say I want to instantiate a protocol between Alice, the issuer on the IOU, and Bob, the payee. Strangely, I can deploy such a protocol by using Bob’s access token on /npl/objects/iou/Iou/ and pass on Alice’s claims as an issuer. But Alice could not agree to owe anything to Bob. How do you make sure this is not possible? Thanks

2

Welcome to our forum!

Right now it is indeed not directly possible to prohibit this.

The usual workaround is to not annotate the constructor with @api and instead use a factory protocol to ensure the IOU is created with the appropriate party bindings.

We recognize that this is not ideal, so we’re working hard on a new feature which allows you to declaratively prevent such assignments. I don’t know the exact timeline, but is should land soon.

3

To add to this, we could implement ways to make sure every party interacts with a protocol before actions can be taken, or restrict the claims that can be used for protocol creation to the ones in the JWT or any other combination. For your use-case of financial agreement, it may be an easy win.

Yet this would very quickly become a constraint for building applications generally. When it is not possible to use a ruleset for automated party assignment and enforcement, modelling the interaction you seek in NPL is best.

For your specific use-case, two additional states will give you the certainty to only have ‘unpaid’ IOUs that actually need to be unpaid. Other implementation may work too.

@api
protocol[issuer, payee] FullyAgreedIou(var forAmount: Number) {
    require(forAmount > 0, "Initial amount must be strictly positive");

    initial state requested;
    state issuerApproved;
    state payeeApproved;
    state unpaid;
    final state paid;
    final state forgiven;

    @api
    permission[issuer] issuerApprove() | requested, payeeApproved {
        if (activeState().getOrFail() == FullyAgreedIou.States.requested) {
            become issuerApproved;
        } else {
            become unpaid;
        };
    };

    @api
    permission[payee] payeeApprove() | requested, issuerApproved {
        if (activeState().getOrFail() == FullyAgreedIou.States.requested) {
            become payeeApproved;
        } else {
            become unpaid;
        };
    }
    // everything else being equall
}
4

This problem can now be solved using Party Automation