activities

 activities  in the ActivityStreams sense represent actions associated with posts, are the content unit of ActivityStreams, and a needlessly more complex (requiring more objects and relations) way to represent posts. In practice activities are an unnecessary abstraction that can be more simply replaced by posts, webmentions, and HTTP based CRUD.

Related

 * http://rhiaro.co.uk/2015/05/generating
 * https://indiewebcamp.com/irc/2015-05-20#t1432135572630