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Date: Thu, 21 Apr 2022 15:20:14 -1000
From: "David A. Harding" <dave@dtrt.org>
To: Matt Corallo <lf-lists@mattcorallo.com>
In-Reply-To: <01d4a034-eb80-a598-1858-6b0ed8295a13@mattcorallo.com>
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Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Automatically reverting ("transitory") soft forks,
 e.g. for CTV
Precedence: list

[Rearranging Matt's text in my reply so my nitpicks come last.]

On 21.04.2022 13:02, Matt Corallo wrote:
> I agree, there is no universal best, probably. But is there a concrete
> listing of a number of use-cases and the different weights of things,
> plus flexibility especially around forward-looking designs?

I'm sure we could make a nice list of covenant usecases, but I don't 
know how we would assign reasonable objective weights to the different 
things purely through group foresight.  I know I'm skeptical about 
congestion control and enthusiastic about joinpools---but I've talked to 
developers I respect who've had the opposite opinions from me about 
those things.  The best way I know of to reconcile our differing 
opinions is to see what real Bitcoin users actually pay for.  But to do 
that, I think they must have a way to use covenants in something like 
the production environment.

> You're also writing off [...] a community of
> independent contributors who care about Bitcoin working together to
> make decisions on what is or isn't the "right way to go" [...]. Why are 
> you
> suggesting its something that you "don't know how to do"?

You said we should use the best design.  I said the different designs 
optimize for different things, so it's unlikely that there's an 
objective best.  That implies to me that we either need to choose a 
winner (yuck) or we need to implement more than one of the designs.  In 
either of those cases, choosing what to implement would benefit from 
data about how much the thing will be used and how much users will pay 
for it in fees.

> Again, my point *is not* "will people use CTV", I think they will. I
> think they would also use TLUV if that were activated for the exact
> same use-cases. I think they would also use CAT+CSFS if that were what
> was activated, again for the exact same use-cases. Given that, I'm not
> sure how your proposal teaches us anything at all, aside from "yes,
> there was demand for *some* kind of covenant".

I'm sorry if my OP was ambiguous about this, but my goal there was to 
describe a general framework for activating temporary consensus changes 
for the purpose of demonstrating demand for proposed features.  I gave 
CTV as an example for how the framework could be used, but we could use 
the same framework to activate APO and TLUV (or IIDs and EVICT)---and 
then we would see which of them people actually used.  If there was 
significant ongoing use of all three after 5 years, great!  We keep them 
all.  If some of them went largely unused, we let the extra validation 
rules expire and move on.

Alternatively, if we only enabled one covenant design (e.g. CTV), we 
would still gain data about how it was used and we could see if some of 
the alternative designs would've been more optimal for those 
demonstrated uses.

My goal here is obtaining data from which we can make informed 
decisions.  A transitory soft fork is an extreme way to acquire that 
data and I fully acknowledge it has several significant problems 
(including those I listed in my OP).  I'm hoping, though, that it's a 
better solution than another activation battle, prolonged yelling on 
this mailing list and elsewhere, or everyone just giving up and letting 
Bitcoin ossify prematurely.  Alternatively, I'm hoping one of the many 
people on this list who is smarter than I am will think of another way 
to obtain decisive data with less fuss.

> Again, you're writing off the real and nontrivial risk of doing a fork
> to begin with.

I agree this risk exists and it isn't my intention to write it off---my 
OP did say "we [must be] absolutely convinced CTV will have no negative 
effects on the holders or receivers of non-CTV coins."  I haven't been 
focusing on this in my replies because I think the other issues we've 
been discussing are more significant.  If we were to get everyone to 
agree to do a transitory soft fork, I think the safety concerns related 
to a CTV soft fork could be mitigated the same way we've mitigated them 
for previous soft forks: heaps of code review/testing and making sure a 
large part of the active community supports the change.

> You don't
> mention the lack of recursion in CTV vs CAT+CSFS

I mentioned recursion, or the lack thereof, in various proposals like 
five times in this thread.  :-)

Thanks again for your replies,

-Dave