Figure 4 uses undefined term

[halindrome]

The figure talks about "Payment instrument"s. I think you mean payment methods, but regardless the terms in the document should be the same as the ones in the other documents in our space.

[msporny]

Hmm, no I think I meant 'payment instrument'. A payment method is "Visa", a "payment instrument" is a "Visa card ending in 7383". The latter is an instantiation of a payment method, which is what you're registering. Does that make sense?

In any case, we may want to get rid of the numbers for the steps.

[halindrome]

It makes sense. And I assume it is defined somewhere... and is consistent with the usage in the other specs in this space?

[msporny]

And I assume it is defined somewhere... and is consistent with the usage in the other specs in this space?

It should be defined in the Web Payments IG glossary. I don't know if it is, I'm in the airport and can't check right now. I think it's consistent with how the group has been using it, but we may want to double check on that. I'll check at some point this week and suggest a PR if it isn't in the WPIG glossary.