Notes on Payment Apps (registration, etc.)

Hi WPWG,

I’ve written up some notes on payment apps for discussion:
 https://github.com/w3c/webpayments/wiki/PaymentApp_Notes

The document is not a spec, but I hope it will facilitate future spec work.

It is a mix of:

 * Definitions
 * A high-level view of payment app registration, display, selection, and invocation with a few requirements sprinkled throughout.
 * A description of what is *not* addressed in this high-level view. I intentionally kept a lot out of the high-level view in the hope
   that we could reach shared understanding on a subset of the questions before resolving some of the trickier pieces.
 * Ideas for how to enable communication between browser and payment app. This bit is the most “out of place” in the
   document since it is lower-level, but I wanted to include it for discussion.

I sprinkled references to group issues throughout the text so that we could see more easily where they fit in.

We plan to discuss payment apps at our 28 April call:
 https://github.com/w3c/webpayments/wiki/Agenda-20160428

Ian

--
Ian Jacobs <ij@w3.org>      http://www.w3.org/People/Jacobs
Tel:                       +1 718 260 9447