Clarity on behaviour with multiple Announce activities for the same object

[evanp]

The Announce activity type is typically used for "share", "retweet", "boost" or "repost" functionality on the social web.

In many social systems, it's reasonable to repost the same object multiple times (for example, a reminder of an upcoming event). Because Mastodon doesn't allow multiple Announce activities, although they're not forbidden in the ActivityPub spec, we need some extra guidance on what to do with repeated Announce activities.

[evanp]

Quoting @trwnh from #384:

Although I have to raise another point of contention: when was it decided that Announce should be idempotent with respect to shares? This is starting to feel like implementation decisions are being raised into the spec itself. For example, if Tumblr decides to implement reblogs as Announce then they will want to support multiple shares most likely. And the original intent with #381 was to clarify cases where a "like" is a kind of post, not a binary signal. This is also why I brought up in #381 that there should be more clarity on the split between a "resource" and a "procedure".

#384 (comment)

[evanp]

I wrote a Primer page on Announce:

https://www.w3.org/wiki/ActivityPub/Primer/Announce_activity

I focused on the interoperability between implementations that expect idempotent shares (one share per object per actor), versus those that allow multiple shares per object per actor.

[nightpool]

Does Mastodon actually disallow multiple announcements? I thought we just had an advisory lock that would deduplicate announcements posted twice in short succession. (EDIT: Actually, I'm not even sure if that exists for Announce like it does for Undo activities)

[nightpool]

(as claimed in the wiki post, just want to make sure we're not publishing misinfo since I haven't actually seen anyone claim anywhere that multiple Announcements are fully disallowed by Mastodon)

…

On Wed, Nov 22, 2023 at 3:14 PM Evan Gilgenbach ***@***.***> wrote: Does Mastodon actually disallow multiple announcements? I thought we just had an advisory lock that would deduplicate announcements posted twice in short succession. On Wed, Nov 22, 2023 at 12:37 PM Evan Prodromou ***@***.***> wrote: > I wrote a Primer page on Announce: > > https://www.w3.org/wiki/ActivityPub/Primer/Announce_activity > > I focused on the interoperability between implementations that expect > idempotent shares (one share per object per actor), versus those that allow > multiple shares per object per actor. > > — > Reply to this email directly, view it on GitHub > <#386 (comment)>, > or unsubscribe > <https://github.com/notifications/unsubscribe-auth/AABZCV7L5OESUNDT73J3AQDYFYZ37AVCNFSM6AAAAAA4N5YGVCVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTQMRTGIYDONRUG4> > . > You are receiving this because you are subscribed to this thread.Message > ID: ***@***.***> >

[evanp]

I'm satisfied with this process, and I think we can follow up in the Primer if we need further discussion.