Sure, I've struggled to find a better way to define it. This is where I am on these definitions:

`resourceType`: The type of the resource in the OAE system
`entityType`: One of actor, object, target. It's the type of the entity associated to the activity.
`objectType`: The type of ActivityObject (as per the ActivityStrea.ms model). This is probably 100% the same as `resourceType`, just different terminology across the specs

I know it's not great.