[Uri-review] Review request for payto URI scheme, draft 01

[Florian Dold <[e-mail]>]

Dear all,

I've submitted a new version of the payto URI scheme draft.

https://datatracker.ietf.org/doc/draft-dold-payto/

The goal of payto:// is to designate payment methods, similar in spirit
to how one would designate electronic mail addresses with the mailto URI
scheme.

Here are the responses and major changes from feedback to the previous
draft that was posted here for review quite some time ago:

Thanks to a suggestion from Eric Wilde, payment methods are now to be
managed in an IANA registry instead of a fixed list within the
specification.

I do not think that currency and amount should be specified in a
separate option.  Separating them would make it look like a payto URI
which only specifies the "amount" option but not the "currency" option
is meaningful.  Since many payment systems support multiple currencies,
the notion of wanting to pay "100" without a currency to some account
creates ambiguity and can be confusing.  One might argue though that
it's possible to require a "currency" option to be present if an
"amount" is specified, which simplifies parsing for consumers of these
URIs, but this also makes them longer and arguably less readable.  I'd
appreciate more feedback here.

David Nicol asked a while back on this list whether we should support
multiple currencies or even a notion of shopping carts.  Since payto://
is intended to address existing payment methods, it is unlikely that
these concepts translate well to them.  Thus I think that the
specification should address the lowest common denominator of payment
systems.  That is also the reason for having a free form "message" field
(intended to be read by humans) that might be changed (encoding / letter
substitution, upper/lower case) and a more limited "instruction" field
that must be preserved verbatim.  These kinds of limitations are common.

These higher level aspects of payments (related to cart management,
shipping addresses, payment method selection and so on) are also already
being addressed by other standards, such as the W3C's Web Payment
Working group.

Best regards,
Florian