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From: Joost Jager <joost.jager@gmail.com>
Date: Thu, 8 Jun 2023 11:16:26 +0200
Message-ID: <CAJBJmV_s_txnaSuZYNwBQv=VvbA6PdFzp7uEKnSNt40LCQDh=w@mail.gmail.com>
To: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
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Subject: Re: [bitcoin-dev] Standardisation of an unstructured taproot annex
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Hi,

In the proposal below, any annex that begins with `0x00` is defined as
free-form. This isn't the most efficient format though because there is
always one byte lost on signalling. In a future where unstructured annex
data turns out to be the predominant use case, this may be relevant. Also
for very short annexes, the lost byte may weigh relatively heavy.

Without sacrificing future extensions to structured annex data, one could
also store the annex data as is except for the case where the data starts
with `0x21` (or any other 'uncommon' byte). If the data starts with `0x21`,
this byte needs to be repeated first and then followed by the remainder of
the data.

Examples:

Data: [01 02 03]
Encoding [01 02 03]

Data: [21 22 23]
Encoding: [21 21 22 23]

The prefixes [21 (not 21)] are available for future upgrades.

Joost

On Fri, Jun 2, 2023 at 5:00=E2=80=AFPM Joost Jager <joost.jager@gmail.com> =
wrote:

> Hi,
>
> As it stands, the taproot annex is consensus valid but non-standard. The
> conversations around standardization seem to be leaning towards the
> adoption of a flexible Type-Length-Value (TLV) format [1]. There's no dou=
bt
> that this approach has considerable potential. However, settling on an
> exact format may require a significant amount of time.
>
> In the interim, the benefits of making the annex available in a
> non-structured form are both evident and immediate. By allowing developer=
s
> to utilize the taproot annex without delay, we can take advantage of its
> features today, without the need to wait for the finalization of a more
> lengthy standardization process.
>
> With this in view, I am proposing that we define any annex that begins
> with '0' as free-form, without any additional constraints. This strategy
> offers several distinct benefits:
>
> Immediate utilization: This opens the door for developers to make use of
> the taproot annex for a variety of applications straight away, thus
> eliminating the need to wait for the implementation of TLV or any other
> structured format.
>
> Future flexibility: Assigning '0'-beginning annexes as free-form keeps ou=
r
> options open for future developments and structure improvements. As we
> forge ahead in determining the best way to standardize the annex, this
> strategy ensures we do not limit ourselves by setting its structure in
> stone prematurely.
>
> Chainspace efficiency: Non-structured data may require fewer bytes
> compared to a probable TLV format, which would necessitate the encoding o=
f
> length even when there's only a single field.
>
> In conclusion, adopting this approach will immediately broaden the
> utilization scope of the taproot annex while preserving the possibility o=
f
> transitioning to a more structured format in the future. I believe this i=
s
> a pragmatic and efficient route, one that can yield substantial benefits =
in
> both the short and long term.
>
> Joost
>
> [1] https://github.com/bitcoin/bips/pull/1381
>

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<div dir=3D"ltr"><div>Hi,</div><div><br></div><div>In the proposal below, a=
ny annex that begins with `0x00` is defined as free-form. This isn&#39;t th=
e most efficient format though because there is always one byte lost on sig=
nalling. In a future where unstructured annex data turns out to be the pred=
ominant use case, this may be relevant. Also for very short annexes, the lo=
st byte may weigh relatively heavy.</div><div><br></div><div>Without sacrif=
icing future extensions to structured annex data, one could also store the =
annex data as is except for the case where the data starts with `0x21` (or =
any other &#39;uncommon&#39; byte). If the data starts with `0x21`, this by=
te needs to be repeated first and then followed by the remainder of the dat=
a.</div><div><br></div><div>Examples:</div><div><br></div><div>Data: [01 02=
 03]</div><div>Encoding [01 02 03]</div><div><br></div><div>Data: [21 22 23=
]</div><div>Encoding: [21 21 22 23]</div><div><br></div><div>The prefixes [=
21 (not 21)] are available for future upgrades.</div><div><br></div><div>Jo=
ost</div><br><div class=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail_att=
r">On Fri, Jun 2, 2023 at 5:00=E2=80=AFPM Joost Jager &lt;<a href=3D"mailto=
:joost.jager@gmail.com">joost.jager@gmail.com</a>&gt; wrote:<br></div><bloc=
kquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:=
1px solid rgb(204,204,204);padding-left:1ex"><div dir=3D"ltr">Hi,<br><br>As=
 it stands, the taproot annex is consensus valid but non-standard. The conv=
ersations around standardization seem to be leaning towards the adoption of=
 a flexible Type-Length-Value (TLV) format [1]. There&#39;s no doubt that t=
his approach has considerable potential. However, settling on an exact form=
at may require a significant amount of time.<br><br>In the interim, the ben=
efits of making the annex available in a non-structured form are both evide=
nt and immediate. By allowing developers to utilize the taproot annex witho=
ut delay, we can take advantage of its features today, without the need to =
wait for the finalization of a more lengthy standardization process.<br><br=
>With this in view, I am proposing that we define any annex that begins wit=
h &#39;0&#39; as free-form, without any additional constraints. This strate=
gy offers several distinct benefits:<br><br>Immediate utilization: This ope=
ns the door for developers to make use of the taproot annex for a variety o=
f applications straight away, thus eliminating the need to wait for the imp=
lementation of TLV or any other structured format.<br><br>Future flexibilit=
y: Assigning &#39;0&#39;-beginning annexes as free-form keeps our options o=
pen for future developments and structure improvements. As we forge ahead i=
n determining the best way to standardize the annex, this strategy ensures =
we do not limit ourselves by setting its structure in stone prematurely.<br=
><br>Chainspace efficiency: Non-structured data may require fewer bytes com=
pared to a probable TLV format, which would necessitate the encoding of len=
gth even when there&#39;s only a single field. <br><br>In conclusion, adopt=
ing this approach will immediately broaden the utilization scope of the tap=
root annex while preserving the possibility of transitioning to a more stru=
ctured format in the future. I believe this is a pragmatic and efficient ro=
ute, one that can yield substantial benefits in both the short and long ter=
m.<br><br>Joost<br><br>[1] <a href=3D"https://github.com/bitcoin/bips/pull/=
1381" target=3D"_blank">https://github.com/bitcoin/bips/pull/1381</a></div>
</blockquote></div></div>

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