@sl007 @humanetech Problem is, the AP spec is deliberately very vague and domain-unspecific. But its real-world implementations are concrete and interpret everything in the context of their domain.
Core properties can be, and often are, also interpreted differently depending on the domain. So in that sense they aren't very much different from extensions many projects declare in their own namespaces, except that they have somewhat similar meanings across implementations.
@sl007 @humanetech So, for example, there's the Follow activity. Everyone knows what that does, right? Wrong.
You can Follow people in a social media service. But you can't in a forum. There you could, for example, follow a topic or a subforum to get notified about new posts. It's two vastly different domains that use the exact same vocabulary in logically incompatible ways.