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Better description of the mainline of a PL event. #1107

Merged
merged 15 commits into from
Jun 15, 2022
Merged

Better description of the mainline of a PL event. #1107

merged 15 commits into from
Jun 15, 2022

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DMRobertson
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@DMRobertson DMRobertson commented Jun 1, 2022

David Robertson added 3 commits June 1, 2022 15:25
``iteratively descending through the `m.room.power_levels` events in the
`auth_events`-starting at *e*.`` was also unclear to me. Unfortunately
this is now more symbol-dense and I'm not sure if it's a net improvement.
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I'm not as convinced by e2d8cfc. I'll leave the reviewer to judge.

@DMRobertson DMRobertson marked this pull request as ready for review June 1, 2022 14:59
@DMRobertson DMRobertson requested a review from a team as a code owner June 1, 2022 14:59
@turt2live turt2live self-requested a review June 1, 2022 15:34
descending through the `m.room.power_levels` events in the `auth_events`
starting at *e*. If no mainline event is encountered when iteratively
descending through the `m.room.power_levels` events, then the closest
Given another event *e* = *e<sub>0</sub>* we can compute a similar list of
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@dkasak dkasak Jun 2, 2022

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The old definition didn't seem to allow for e (e_0) itself to be the closest mainline event to e, but the new one seems to allow it. Is this correct?

Also, is e meant to be an arbitrary event here or another m.room.power_levels event?

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Not sure, I'll consider this more carefully.

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@DMRobertson DMRobertson Jun 6, 2022

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The old definition didn't seem to allow for e (e_0) itself to be the closest mainline event to e, but the new one seems to allow it. Is this correct?

I think there is some leeway here. What matters is that part (1) of the mainline ordering is unchanged (we don't use this notion of closest mainline event anywhere else AFAICS).

Also, is e meant to be an arbitrary event here or another m.room.power_levels event?

I think e is arbitrary, including the possibility that e is another m.room.power_levels event.

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I think there is some leeway here. What matters is that part (1) of the mainline ordering is unchanged (we don't use this notion of closest mainline event anywhere else AFAICS).

The idea I had was: what if e is a m.room.power_levels event itself and it has no m.room.power_levels in its auth_events? Then e would be the closest mainline event to e according to the new definition, but not according to the old one.

In any case, looks to me like you fixed the concern in the new version 👍🏻

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Then e would be the closest mainline event to e according to the new definition, but not according to the old one.

Agreed. And I think that change would be a mistake. My rough sense of this is that we're trying to see where e fits into the history of power level events, so that "older" events are ordered first.

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@DMRobertson DMRobertson marked this pull request as draft June 5, 2022 23:39
DMRobertson and others added 3 commits June 6, 2022 12:50
This has undergone a fairly large rework, so needs careful inspection.
looks better in Firefox. I am sad to be writing a poor man's TeX though.
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I have rewritten things more dramatically; this needs careful interrogation,

https://pr1107--matrix-spec-previews.netlify.app/rooms/v9/#definitions for the rendered view.

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I can't request reviewers, but I'd also appreciate @erikjohnston here

@DMRobertson DMRobertson marked this pull request as ready for review June 6, 2022 13:27
@DMRobertson DMRobertson requested a review from dkasak June 6, 2022 13:27
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Left some minor suggestions, but overall this reads much more clearly to me and is a definite improvement over the current situation. I also believe it is a correct translation of the original text, but I'd love Erik to see it too.

event in its `auth_events`.
The *mainline of P*<sub>0</sub> is the list of events
[*P*<sub>n</sub> , ... , *P*<sub>1</sub>, *P*<sub>0</sub>],
ordered from oldest to newest.
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The implicit reference to time in the form of "oldest and newest" is throwing me here a bit. Perhaps this?

Suggested change
ordered from oldest to newest.
ordered such that the indices are descending, so that the event we started with is last.

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For what it's worth: each $P_i$ cites $P_{i+1}$ as an auth event. So the latter is "older" in some sense... but it's not necessarily "older" in the sense implied by the prev_events edges, or "older" as determined by origin_server_ts or even received_ts. So I agree that "older" is more trouble than it's worth.

However: now that we have explicit indices that the text later refers to, I'd be tempted to just write it out starting with $P_0$ and let indices increase.

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I think this comment thread is outdated. The current wording includes explicit indexes and is clear for me.

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much improved for sure! Some minor suggestions

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@DMRobertson DMRobertson requested a review from richvdh June 14, 2022 17:17
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Co-authored-by: Richard van der Hoff <[email protected]>
@turt2live turt2live dismissed their stale review June 14, 2022 17:40

addressed

@DMRobertson DMRobertson requested a review from richvdh June 15, 2022 14:55
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lgtm!

@richvdh richvdh merged commit 2ee2172 into matrix-org:main Jun 15, 2022
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The description of a power-levels event's mainline is unclear
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