I think the #ActivityPub client-to-server API is extremely important and underrated.
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@smallcircles @evan @julian if only the application domain of activitystreams was activities and streams...
i do think it causes a lot of confusion to stray away from activities as content, instead using them as vehicles for state changes (which will never be consistent, not even eventually consistent).
back when atompub and atom+as1 were a thing, the "feed entry" was atom semantics and the "activity stream" was as1 semantics. they coexisted in the same xml file. it worked well enough.
Yes, for the ideation on Protosocial as an #ActivityPub compliant extension (going back to the roots with blank slate W3C specs) I imagined mapping the AS primitives to consistent protocol capabilities and thereby define a set of normative architecture patterns, like "this is how we do CRUD, this is Publish/Subscribe, this is an Event stream and this a Collection", etc.
Then Protosocial library and SDK implementers would need to deal with #ActivityStreams at a low-level plumbing impl detail, while solution developers would have a higher-level API to invoke these patterns. And other than that would not need to touch #ActivityStreams which is now entirely reserved to making AP work on the wire.
A combination of linked data practices and schema-based design would be used for both open-world and closed-world extension modeling. But here too the solution developer should be shield from the nitty gritty internal mechanics.
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@evan @julian@fietkau.social @julian@activitypub.space @smallcircles anyway, to address julian (not lam)'s question: what does Accept(Note) even mean? what does it entail? can you always assume it has to do something with a replies collection that may or may not be there?
@trwnh That's kinda what I'm getting at, yeah. The goal is to express that the owner of the replied-to object has accepted a reply, i.e. that the reply is added to the post's replies collection and shown under it in the web view. Followers and other observers are made aware this reply is accepted and can be shown similarly in other places that want to honor the poster's reply filters, so observers don't need to iterate over the replies collection all the time.
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@trwnh That's kinda what I'm getting at, yeah. The goal is to express that the owner of the replied-to object has accepted a reply, i.e. that the reply is added to the post's replies collection and shown under it in the web view. Followers and other observers are made aware this reply is accepted and can be shown similarly in other places that want to honor the poster's reply filters, so observers don't need to iterate over the replies collection all the time.
@trwnh The GTS interaction controls docs mention the replies collection, but only tangentially. For the purpose of conversation backfilling (which GTS doesn't do yet) I'm wanting to emphasize that the replies collection is the source of truth for replies curated by the object owner.
The Accept(Note) is essentially a hack to allow interactions from servers that don't implement GTS's ReplyRequest activity. I'll discuss with them how best to signal reply acceptance.
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@trwnh The GTS interaction controls docs mention the replies collection, but only tangentially. For the purpose of conversation backfilling (which GTS doesn't do yet) I'm wanting to emphasize that the replies collection is the source of truth for replies curated by the object owner.
The Accept(Note) is essentially a hack to allow interactions from servers that don't implement GTS's ReplyRequest activity. I'll discuss with them how best to signal reply acceptance.
@julian@fietkau.social @evan @julian@activitypub.space @smallcircles
> express that the owner of the replied-to object has accepted a reply, i.e. that the reply is added to the post's replies collection and shown under it in the web view
i get that, but the question is whether you can claim this understanding universally for all peers. as it stands, Accept is very vague wrt this. Accept(Note) meaning "Add to replies collection" might be a thing gts does, but that's their interpretation of Accept, not the definition.
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@julian@fietkau.social @evan @julian@activitypub.space @smallcircles
> express that the owner of the replied-to object has accepted a reply, i.e. that the reply is added to the post's replies collection and shown under it in the web view
i get that, but the question is whether you can claim this understanding universally for all peers. as it stands, Accept is very vague wrt this. Accept(Note) meaning "Add to replies collection" might be a thing gts does, but that's their interpretation of Accept, not the definition.
@julian@fietkau.social @evan @julian@activitypub.space @smallcircles
> replies collection is the source of truth for replies curated by the object owner.
this is fine i think, but the way to do this usually is HTTP GET. you could notify of changes to the replies collection, or you could reify the Reply and then Accept that?
the Reply has an instrument which is the Note. it has clear side effects to Add the instrument to the object.replies. the side effects can be gated behind Accept/Reject like following currently works.
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@julian@fietkau.social @evan @julian@activitypub.space @smallcircles
> replies collection is the source of truth for replies curated by the object owner.
this is fine i think, but the way to do this usually is HTTP GET. you could notify of changes to the replies collection, or you could reify the Reply and then Accept that?
the Reply has an instrument which is the Note. it has clear side effects to Add the instrument to the object.replies. the side effects can be gated behind Accept/Reject like following currently works.
@julian@fietkau.social @evan @julian@activitypub.space @smallcircles alternatively add the Reply itself, parallel to likes/shares collections. it depends on whether you think the replies collection should always contain a specific type of object, which i don't think is something you can guarantee because publishers can do anything with it. similar to how some publishers include activities in threads and some include notes.
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@julian@fietkau.social @evan @julian@activitypub.space @smallcircles alternatively add the Reply itself, parallel to likes/shares collections. it depends on whether you think the replies collection should always contain a specific type of object, which i don't think is something you can guarantee because publishers can do anything with it. similar to how some publishers include activities in threads and some include notes.
@julian@fietkau.social @evan @julian@activitypub.space @smallcircles i think the issue here is that projects are doing things that may or may not get widely adopted, then if the proposals ever change, they have to deal with older software only understanding the old thing they tried. (this is where i would say something about protocol capability negotiation)
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@julian@fietkau.social @evan @julian@activitypub.space @smallcircles
> express that the owner of the replied-to object has accepted a reply, i.e. that the reply is added to the post's replies collection and shown under it in the web view
i get that, but the question is whether you can claim this understanding universally for all peers. as it stands, Accept is very vague wrt this. Accept(Note) meaning "Add to replies collection" might be a thing gts does, but that's their interpretation of Accept, not the definition.
@trwnh This is in the context of a FEP draft which prescribes a meaning (including desired side effects) for compliant implementations.
Hence my fidgeting with the vocabulary. The effects are the goal, the question is how they should be expressed and broadcasted. (Principle of least surprise, potential compatibility with existing implementations that look at the replies collection, concerns around server traffic...)
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@julian@fietkau.social @evan @julian@activitypub.space @smallcircles i think the issue here is that projects are doing things that may or may not get widely adopted, then if the proposals ever change, they have to deal with older software only understanding the old thing they tried. (this is where i would say something about protocol capability negotiation)
@trwnh There's also this, yeah. GTS interaction controls have already gone through one breaking schema revision from version 0.19 to 0.21 (with 0.20 trying to manage both), and a core goal of the FEP I'm working on is to not break compatibility again.
Sending out an Add in addition to the Accept(Note) that's already happening should be non-breaking for existing implementations, I'm pretty sure. What's left to decide is whether it's a good idea.
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@trwnh There's also this, yeah. GTS interaction controls have already gone through one breaking schema revision from version 0.19 to 0.21 (with 0.20 trying to manage both), and a core goal of the FEP I'm working on is to not break compatibility again.
Sending out an Add in addition to the Accept(Note) that's already happening should be non-breaking for existing implementations, I'm pretty sure. What's left to decide is whether it's a good idea.
@julian@fietkau.social @evan @julian@activitypub.space @smallcircles this makes me really wish people didn't overload the AS2 vocab so much, and were less afraid of defining their own extensions. you could swing it so that the same activity is an Add, Accept, and ReplyAck. it sucks that we have to pick one instead of using whatever makes sense. (developers: please support multityping and/or duck typing! composability is the only true path to extensibility, and one size never fits all...)
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@trwnh There's also this, yeah. GTS interaction controls have already gone through one breaking schema revision from version 0.19 to 0.21 (with 0.20 trying to manage both), and a core goal of the FEP I'm working on is to not break compatibility again.
Sending out an Add in addition to the Accept(Note) that's already happening should be non-breaking for existing implementations, I'm pretty sure. What's left to decide is whether it's a good idea.
@julian@fietkau.social in a parallel conversation not about interaction controls, @rimu@piefed.social made the case for batching events, which I'm going to repurpose as an argument against sending additional activities for backward compatibility (unless absolutely necessary.)
> As a user can do a great number of notable things (posting content, liking content, following others) each minute and there can be thousands of instances to send to, a great many POST requests can be sent in a short amount of time.
>
> For example if 5 people cast 20 votes and there are 500 instances, the instance hosting the community containing the posts being voted on must send 5 * 20 * 500 = 50,000 HTTP POSTs. -
@julian@fietkau.social @evan @julian@activitypub.space @smallcircles this makes me really wish people didn't overload the AS2 vocab so much, and were less afraid of defining their own extensions. you could swing it so that the same activity is an Add, Accept, and ReplyAck. it sucks that we have to pick one instead of using whatever makes sense. (developers: please support multityping and/or duck typing! composability is the only true path to extensibility, and one size never fits all...)
@julian@fietkau.social @evan @julian@activitypub.space @smallcircles
actor: alice
type: as:Accept, as:Add, _:ReplyAck
object: <the reply>
target: <the replies collection>
_:postRepliedTo: <op>for the Accept, you need to understand it as "accepting the object into the target", which is apparently a thing in AS2-Vocab.
for the Add, you need to understand it as Add is defined -- no surprises there, i think?
for the ReplyAck, it can be whatever you define. here i've used an extension postRepliedTo property.
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@julian@fietkau.social @evan @julian@activitypub.space @smallcircles
actor: alice
type: as:Accept, as:Add, _:ReplyAck
object: <the reply>
target: <the replies collection>
_:postRepliedTo: <op>for the Accept, you need to understand it as "accepting the object into the target", which is apparently a thing in AS2-Vocab.
for the Add, you need to understand it as Add is defined -- no surprises there, i think?
for the ReplyAck, it can be whatever you define. here i've used an extension postRepliedTo property.
@trwnh The GTS implementation comes with a vocabulary extension, so adding another activity type would be an option.
I guess the reason they didn't do that for this case (I wasn't around for the decision) is that the Accept(Note) thing is itself a backward compatibility hack that they hoped to be able to drop eventually, when more servers would send ReplyRequests (which can be Accept-ed directly), and adding a new type would have felt too much like “enshrining” it.
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@julian@fietkau.social in a parallel conversation not about interaction controls, @rimu@piefed.social made the case for batching events, which I'm going to repurpose as an argument against sending additional activities for backward compatibility (unless absolutely necessary.)
> As a user can do a great number of notable things (posting content, liking content, following others) each minute and there can be thousands of instances to send to, a great many POST requests can be sent in a short amount of time.
>
> For example if 5 people cast 20 votes and there are 500 instances, the instance hosting the community containing the posts being voted on must send 5 * 20 * 500 = 50,000 HTTP POSTs.@julian@activitypub.space I'm doing my best to realistically prioritize traffic load as well, yeah. The case of accepting an incoming reply will be frequent, whereas the one where you first accept a reply, then change your mind and revoke the acceptance, would be expected to be relatively rare.
The easy way out for me would be to just not touch that part of the spec, leave it as Accept(Note), and see what implementers do with it.
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@trwnh The GTS implementation comes with a vocabulary extension, so adding another activity type would be an option.
I guess the reason they didn't do that for this case (I wasn't around for the decision) is that the Accept(Note) thing is itself a backward compatibility hack that they hoped to be able to drop eventually, when more servers would send ReplyRequests (which can be Accept-ed directly), and adding a new type would have felt too much like “enshrining” it.
@julian i think mastodon handles multityping in certain code paths but most other projects don't. it could have been a compatibility thing?
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@julian i think mastodon handles multityping in certain code paths but most other projects don't. it could have been a compatibility thing?
@trwnh Maybe. I have no idea if GTS itself can handle activities with multiple types.
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Except when they are called other names instead
A timeline is a different thing than a collection imho. And an AS collection has some very particular functionality, which if I model a timeline in my app may not supported (e.g. reverse ordering).
Collection / 'timeline' is one of those words where sometimes they indicate an app domain, and sometimes a core protocol mechanism. Same is true with 'follow' which is sometimes a user action, sometimes indicates low-level publish/subscribe.
For core capabilities that must be part of the specs, in 'protocol space' it may be better to use terminology that is more common in messaging architectures and all the various architecture patterns that are involved. Perhaps idk we deal with a time-ordered event log or something like that.
@smallcircles @evan An AS2 Collection cannot be a timeline (in general). It’s not even ordered. An AS2 OrderedCollection (a subtype of Collection) might be ordered by time or not, so it’s also not a timeline (in general). When they are ordered by some time value (unspecified in AP) they are often called “streams” in the spec. The Mastodon content timelines are not the same as AP activity streams although a filtered AP stream can be transformed to a content timeline.
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@smallcircles @evan An AS2 Collection cannot be a timeline (in general). It’s not even ordered. An AS2 OrderedCollection (a subtype of Collection) might be ordered by time or not, so it’s also not a timeline (in general). When they are ordered by some time value (unspecified in AP) they are often called “streams” in the spec. The Mastodon content timelines are not the same as AP activity streams although a filtered AP stream can be transformed to a content timeline.
@steve I think
we need to emphasize that timelines can be built from regular collections, even unordered ones, by using some intermediate representations specific to the type of timeline that a client wants to render.The fact that the specification does not directly support a mapping between a collection and a responsive timeline, *DOES NOT MEAN* one can't be built from it, only that it requires a little more effort on the client side.
My goto example is how rich mail clients allow responsive mailbox representations on top of a much less expressive collection method that IMAP provides compared to ActivityPub.
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@steve I think
we need to emphasize that timelines can be built from regular collections, even unordered ones, by using some intermediate representations specific to the type of timeline that a client wants to render.The fact that the specification does not directly support a mapping between a collection and a responsive timeline, *DOES NOT MEAN* one can't be built from it, only that it requires a little more effort on the client side.
My goto example is how rich mail clients allow responsive mailbox representations on top of a much less expressive collection method that IMAP provides compared to ActivityPub.
@mariusor @smallcircles @evan I’m not sure I completely follow. A timeline is ordered by time. I agree that an unordered collection could be sorted by time to create a timeline. The AP OrderedCollection “stream” is a kind of rigid presorting that anticipates what an AP client would want. However, I also agree that even those could be reordered (by time or otherwise) and/or filtered in the client to provide custom views of the activity stream.
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@mariusor @smallcircles @evan I’m not sure I completely follow. A timeline is ordered by time. I agree that an unordered collection could be sorted by time to create a timeline. The AP OrderedCollection “stream” is a kind of rigid presorting that anticipates what an AP client would want. However, I also agree that even those could be reordered (by time or otherwise) and/or filtered in the client to provide custom views of the activity stream.
@steve yes, that's how I meant it. A client fetches as much of the collection as it can, then applies whatever rules it wants to transform the result into a "timeline" when the user asks for it.
This however most likely requires local caching of the collection to have decent latency.
