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From: Lloyd Fournier <lloyd.fourn@gmail.com>
Date: Mon, 5 Apr 2021 10:35:14 +1000
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To: Andrew Chow <achow101-lists@achow101.com>, 
 Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
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Subject: Re: [bitcoin-dev] New PSBT version proposal
Precedence: list

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On Wed, 10 Mar 2021 at 11:20, Lloyd Fournier <lloyd.fourn@gmail.com> wrote:

> Hi Andrew & all,
>
> I've been working with PSBTs for a little while now. FWIW I agree with the
> change of removing the global tx and having the input/output data stored
> together in the new unified structures.
>
> One thing I've been wondering about is how output descriptors could fit
> into PSBTs. They are useful since they allow you to determine the maximum
> satisfaction weight for inputs so you can properly align fees as things get
> added. I haven't seen any discussion about including them in this revision.
> Is it simply a matter of time before they make it into a subsequent PSBT
> spec or is there something I'm missing conceptually?
>


Sipa replied to me off list some time ago and explained what I was missing.
PSBTs have all the information you could want from a descriptor already.
For example the maximum satisfaction weight can be determined from the
witness/redeem script (I had forgot these fields existed). Therefore
descriptors are more useful in higher level applications while PSBTs are
useful for communicating with signing devices. Therefore there is no reason
for PSBTs to support descriptors.

LL

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote">=
<div dir=3D"ltr" class=3D"gmail_attr">On Wed, 10 Mar 2021 at 11:20, Lloyd F=
ournier &lt;<a href=3D"mailto:lloyd.fourn@gmail.com">lloyd.fourn@gmail.com<=
/a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0=
px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><=
div dir=3D"ltr"><div>Hi Andrew &amp; all,</div><div><br></div><div>I&#39;ve=
 been working with PSBTs for a little while now. FWIW I agree with the chan=
ge of removing the global tx and having the input/output data stored togeth=
er in the new unified structures.</div><div><br></div><div>One thing I&#39;=
ve been wondering about is how output descriptors could fit into PSBTs. The=
y are useful since they allow you to determine the maximum satisfaction wei=
ght for inputs so you can properly align fees as things get added. I haven&=
#39;t seen any discussion about including them in this revision. Is it simp=
ly a matter of time before they make it into a subsequent PSBT spec or is t=
here something I&#39;m missing conceptually?</div></div></blockquote><div><=
br></div><div><br></div><div>
Sipa replied to me off list some time ago and explained what I was missing.=
 PSBTs have all the information you could want from a descriptor already. F=
or example the maximum satisfaction weight can be determined from the witne=
ss/redeem script (I had forgot these fields existed). Therefore descriptors=
 are more useful in higher level applications while PSBTs are useful for co=
mmunicating with signing devices. Therefore there is no reason for PSBTs to=
 support descriptors.<br></div><div><br></div><div>LL<br></div><div><br></d=
iv><br></div></div>

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