Post and Activity types

Recently I've been trying to wrap my head around the implicit vs. explicit post types debate (in the Social Web WG, indieweb community, and elsewhere). Here is some analysis of the different perspectives, and report on my own experiences so far.


I think each side of the debate about explicit vs implicit types are misaligned, due to conflation of Objects and Activities. I think Objects (like blogposts) needn't have explicit types, but Activities (like the act of creating a post) should do.

Thanks to Tantek, Aaron, elf Pavlik, Chris and everyone whose conversations I've listened in on in #social and #indiewebcamp IRC channels for discussing this stuff with/around me.

Indieweb: focus on UI

Indieweb development starts with thinking about UI. The reason for thinking about different kinds of posts comes from a desire to display some posts differently to others. But rather than declaring them outright, one can infer how to display them based on the properties of a post (see also IndieWeb Posts by aaronpk.

"explicit post/object types are architecture-centric design, rather than user-centric design" - tantek, #indiewebcamp irc

Posting UI

Another rationale against explicit post types is that it encourages posting clients to constrain users regarding what kind of posts they can create.

"...content types dictate the kinds of content you actually allow people to create with your software" - benwerd, The tyranny of content types

Most mainstream social networks now have a generic posting interface, that allows one to add things like photos, videos, people tags, etc, without forcing you to choose what type of post you want to make first.

Software architecture

Some people started with explicit post types and ran into problems when structuring their software around this idea. TODO: Citation from aaronpk in irc in March/April that I can't find right now.

URL design

If you include a slug for a post type in your URLs and decide to change the post type, this is definitely a pain. I figured this pretty early and dropped it from Slog'd. See also: Update URL Scheme issue for p3k.

On the other hand:

"but including type [in URL] because I like clustering by type in a day" - tantek, #indiewebcamp irc

... which I think relates to querying, discussed later.

Clarification: content-based vs intent-based post types

Often photo-type-post vs article-type-post is thrown up: ie. if you start with an article, then edit it to add a photo, does the post type change? I completely agree that typing based on content doesn't make sense here. When I talk about post types, I'm referring to types for like, bookmark, repost, log/metrics (eg. food, sleep), where they may look like a note in terms of content, but aren't. I display different icons for all of these at the moment, and you'll note that twitter for example displays retweets differently in the timeline.

Post all the things

Conclusion: in the indieweb community, so far, everything created is considered a post (a h-entry in microformats), and display differences can be inferred from properties of the post.


ActivityStreams2.0 has explicit object types and explicit activity types. It's easy to conflate them; I think this is what is happening when discussing types in AS2 with indieweb people, and I certainly had this problem for a while.

Taking an action generates an Activity, which might result in an Object (like a post).

Beyond posts

Contrary to indieweb stuff so far, AS2 allows for the idea that not every action on the social web results in a post. Having been immersed in indieweblogworld for ages, this was briefly a hard sell, but then I started to think of social actions (activites) I might want to take - that it's reasonable to want to publish in a feed - that I probably don't need to create a post for. Eg:

I don't publish any of these activities on my site yet. There are some activities I do publish with posts (or plan to imminently), that don't necessarily (I might need convincing on some fronts) need to be posts:

Activities vs objects

An Activity can be generated for any action.

I strongly feel that all Activity should have URIs so that if it doesn't result in a post, it can still be interacted with (eg. you can like my edit). (However, this presents another point for confusion: when do I like a post, and when do I like the fact you published it (the create activity). Anyway, this is for another time..).

Since activities are generated as a result of an action, not explicitly created by a user (unlike objects), arguments for not explicitly typing them fall down:

If you want to generate an activity stream from your actions, we do get an additional argument for explicit types of objects: it makes it much easier to generate a suitable Activity.


Explicit types for objects or activities make it easy to query by type. Inferring types - particularly from a combination of properties - complicates this a lot. I recently temporarily dropped quicklinks to /articles and /notes in Slogd after removing sioc:BlogPost and sioc:MicroblogPost as explicit post types made it suddenly more complicated to get them. Given a stream of many people's activities from all over the place how do you filter for specific things?

Human-friendly display

Displaying an activity (the fact that someone did something) is different to displaying an object. You might want to form a sentence ("alice likes bob's tweet") without caring what the properties of the object or possible result are. It's easier to figure out how to display it if it just has a type, without needing to follow links to the object or possible result to infer what's going on.

Generating activity streams

I guess... If you want to take a bunch of objects and generate an activity stream from them, and they don't have explicit types, it's totally up to you (an implementation detail, aka plumbing) how you decide what types the corresponding Activitys have.

I'm not sure if it would be nice to have something in the AS2.0 spec to help with consistently deciding how to infer activity types from object properties. Maybe it doesn't matter.

...Wait, is this ISSUE-4? Lack of explicit mention of activities or objects makes it hard to tell.



  1. I should probably generate an AS2.0 feed from my posts.
  2. Start integrating non-post-resulting activities into it.

Other notes

I went through the lists of Activity types and Object types in current draft of AS2.0 vocab and did a first pass at things I am using, might use and probably won't use. I'll publish this in another post.

I drew lots of diagrams of how I'd turn my different types of posts into Activitys based on their properties (how I'd infer activity types from object properties). I'll also type these up for another post.

Activity is a subclass of Object in AS2. Practical and conceptual differences could be discussed in more depth, but include things like ephemerality of activities vs objects.

Further discussion (possibly):

🏷 activities activitystreams2.0 activitystreams feed hacking indieweb mf2 microformats2 post types social web

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