From: Drak <drak@zikula•org>
To: Mike Hearn <mike@plan99•net>
Cc: Bitcoin Dev <bitcoin-development@lists•sourceforge.net>,
Stephane Brossier <stephane@kill-bill•org>,
Pierre-Alexandre Meyer <pierre@kill-bill•org>
Subject: Re: [Bitcoin-development] Extension for BIP-0070 to support recurring payments
Date: Tue, 25 Feb 2014 18:40:03 +0000 [thread overview]
Message-ID: <CANAnSg3LF6m9u-MV8XiiomMPrbihJh7hm5o=menOWY71bLkdAg@mail.gmail.com> (raw)
In-Reply-To: <CANEZrP0-LqFC8N500=mnKbKE+=UtFw_Y5cHR8JRC-zmmGsSAjA@mail.gmail.com>
[-- Attachment #1: Type: text/plain, Size: 6759 bytes --]
Forgive me if I missed it, but the spec doesnt look like it can handle only
handle periods of per week, per month, per quarter rather than 'n period'.
I take Paypal as a reference example for subscription payments where you
can set recurring to every: n days, n weeks, n months, n years. That way a
quarterly payment is every 3 months. This fine granularity is necessary
because sometime a payment scheme can be per 4 weekly rather than per
monthly.
So in summary the spec needs daily as an option, and to specify the
recurring cycle as every n*period (one of daily, weekly, monthly, yearly):
and you can drop quarterly since it's just expressed as per 3*monthly.
Drak
On 25 February 2014 16:29, Mike Hearn <mike@plan99•net> wrote:
> Hey there,
>
> So the essence of this protocol is as follows:
>
> enum PaymentFrequencyType {
>
> WEEKLY = 1;
>
> MONTHLY = 2;
>
> QUARTERLY = 3;
>
> ANNUAL = 4;
> }
> message RecurringPaymentDetails {
> // Namespace for the merchant such as org.foo.bar
>
> required string merchant_id = 1;
>
> // Id for the recurring subscription
> required bytes subscription_id = 2;
>
> // Contracts associated with a given subscription
>
> repeated RecurringPaymentContract contracts = 3;
>
> }
> message RecurringPaymentContract {
>
> // Unique id for a given contract
>
> required bytes contract_id = 1;
>
> // URL to poll to get the next PaymentRequest
>
> required string polling_url = 2;
>
> // Timestamp; when this contract starts
> required uint64 starts = 3;
>
> // Timestamp; when this contract should be considered invalid
>
> optional uint64 ends = 4;
>
> // Expected payment frequency
> optional PaymentFrequencyType payment_frequency_type = 5;
>
> // Max payment amount within that frequency (e.g. no more than 5 BTC per month)
>
> optional uint64 max_payment_per_period = 6;
>
> // Max payment amount (e.g. no more than 3 BTC per payment)
>
> optional uint64 max_payment_amount = 7;
>
> }
>
> I have the following comments:
>
> 1. There's no need to serialize RecurringPaymentDetails as bytes here.
> It's done that way outside of PaymentDetails in order to support digital
> signatures over protobufs that may have extensions the wallet app isn't
> aware of, but it's a pain and inside PaymentDetails (and therefore for most
> extensions) it shouldn't be necessary. So you can just use "optional
> RecurringPamentDetails recurring_payments = 8;"
>
> 2. There's only 4 possibilities here for recurrences. That seems
> rather restrictive. Is the cost of being more expressive really so high?
> Why not allow more flexible specification of periods?
>
> 3. If there's no payment_frequency_type field then what happens? A
> quirk of protobufs to be aware of is that making an enum field "required"
> can hurt backwards compatibility. Because it will be expressed using a
> languages underlying enum type, if there's a new enum member added later
> old software that attempts to deserialize this will throw exceptions
> because the new "unknown" member would be unrepresentable in the old model.
> Making the field optional avoids this problem (it will be treated as
> missing instead) but means software needs to be written to know what to do
> when it can't read the enum value / sees enum values from the future.
>
> 4. I assume the amounts are specified in terms of satoshi, and
> timestamps are UNIX time, but better to make that explicit.
>
> 5. Seems there's an implicit value constraint that max_payment_amount
> <= max_payment_per_period. What happens if that constraint is violated?
> Best to document that.
>
> 6. What's the "merchant ID" namespace thing about? What's it for? What
> happens if I set my competitors merchant ID there?
>
> 7. What's the "subscription ID"? Is this stuff not
> duplicative/redundant with the existing merchant_data field?
>
> 8. In what situations would you have >1 contract per payment request?
> I'm not sure I understand why it's repeated. Presumably if there are zero
> contracts included the data should be ignored, or an error thrown and the
> entire payment request rejected? Which should it be?
>
> 9. It's unclear to me given such a contract when the payment should
> actually occur. For instance if it's "monthly" then what day in the month
> would the payment occur?
>
> 10. You'll notice I moved the comments to be above the field
> definitions. I know the current proto isn't done that way, but let's change
> it - long comments are good and putting them above the field definitions
> encourages people to write enough detail without being put off by line
> length constraints
>
>
> I think the next step would be to talk to BitPay/get Jeff+Stephen involved
> because I know they have customers that really want recurring payments, and
> those guys will have a clearer idea of customer requirements than we do. I
> feel uncomfortable with designing or reviewing in a vacuum without some
> actual people who would use it chiming in, as I don't really know much
> about the underlying business processes.
>
> I have some other comments about the bitcoinj implementation specifically
> - for instance, we don't have a "wallet directory" concept: everything goes
> into the wallet file. So we'll need to think about how to structure the
> code to allow that. Also, just using a background polling thread is likely
> not flexible enough, as on some platforms you can't stay running all the
> time (e.g. Android) without upsetting people, but the underlying OS can
> wake you up at the right times, so wallet apps should have an ability to
> control wakeup tasks. But we can discuss that over on the bitcoinj list
> specifically. Let's keep this thread for the general protocol design.
>
> BIP 70 is indeed implemented in Bitcoin Core on the C++ side, so that
> isn't a concern. It could be done there too.
>
>
>
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next prev parent reply other threads:[~2014-02-25 18:48 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-28 2:36 Stephane Brossier
2014-01-28 3:58 ` Kevin Greene
2014-01-28 4:29 ` Jeff Garzik
2014-01-28 4:43 ` Jeff Garzik
2014-01-28 5:07 ` PikaPay
2014-01-28 6:08 ` Odinn Cyberguerrilla
2014-01-28 6:48 ` Jeff Garzik
2014-01-28 6:34 ` Mike Hearn
2014-01-29 2:47 ` Stephane Brossier
2014-01-31 18:13 ` Mike Hearn
2014-02-08 2:57 ` Stephane Brossier
2014-02-09 2:48 ` Stephane Brossier
2014-02-11 10:00 ` Kevin Greene
2014-02-11 18:01 ` Stephane Brossier
2014-02-12 6:32 ` Kevin Greene
2014-02-12 6:37 ` Kevin Greene
2014-02-14 20:28 ` Stephane Brossier
2014-02-24 18:04 ` Stephane Brossier
2014-02-25 16:29 ` Mike Hearn
2014-02-25 18:40 ` Drak [this message]
2014-02-25 19:03 ` Jeremy Spilman
2014-02-25 19:06 ` Christophe Biocca
2014-02-26 3:53 ` Stephane Brossier
2014-02-26 10:30 ` Mike Hearn
2014-02-11 16:24 ` Mike Hearn
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