In the Detailed Payment Flow Section, steps 5, 6, and 7 are intended to provide for various flows envisioned by the Web Payments ecosystem. This algorithm is merely a starting point, is very much a work in progress, and is not asserted to be correct at present:

1. Let "selectedApp" be the payment app selected by the payment mediator.
2. Let "selectedMethod" be the payment method provided by the payee and selected by the payer.
3. If selectedMethod.paymentRequestService exists, re-direct the user there (payee-based PSP).
4. If selectedApp.paymentRequestService exists, re-direct the user there (payer-based PSP).
5. Otherwise, the payment response can be generated locally (local PSP - Bitcoin and others).