%% You should probably cite draft-vauban-x402-vpsf-algebra-01 instead of this revision.
@techreport{vauban-x402-vpsf-algebra-00,
    number =    {draft-vauban-x402-vpsf-algebra-00},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-vauban-x402-vpsf-algebra/00/},
    author =    {Vauban Research},
    title =     {{VPSF Claim Algebra for x402 Payment Receipts}},
    pagetotal = 20,
    year =      2026,
    month =     may,
    day =       24,
    abstract =  {The x402 protocol ({[}X402-V2{]}) defines three wire messages for HTTP- native payment flows but provides no composability model for payment receipts. A recipient holding a SettlementReceipt and a DelegationGrant cannot natively express that the settlement satisfies a delegated spending condition, or that a RefundClaim negates an earlier SettlementReceipt, without bespoke facilitator-side logic. As automated payment pipelines grow, the absence of a normative composability layer leads to fragmented, non-interoperable verification surfaces. This document specifies the Vauban Proof Stack Framework (VPSF) Claim Algebra for x402 payment receipts: a grammar of five composition operators (Conjunction, Implication, Aggregation, Selective Disclosure, Revocation; abbreviated ∧, \(\rightarrow\), ⊕, ▷, ¬) applied over the four canonical Payment Claim types (PaymentIntent, SettlementReceipt, RefundClaim, DelegationGrant) defined in {[}LIFECYCLE-FSM{]}. The algebra is chain-agnostic by invariant; the Starknet-based proof system described in {[}STARK-RECEIPTS{]} is the first reference implementation. Composability is grounded in the JCS canonical preimage discipline ({[}RFC8785{]}), ensuring operator results are deterministic and cross-implementation consistent. An open-source Rust implementation is provided in {[}VAUBAN-CRATE{]}.},
}