[rules-users] ruleflow-group vs. agenda-group vs. activation-group ?

Hi All, I've been experimenting with agenda-group and ruleflow-group features and I am now a bit confused. The documentation states that agenda-group and ruleflow-group features have been merged, but I'm not sure how this relates to activation groups. ruleflow-groups used to be a rule-flow feature, driven by the .RF file, requiring JBPM engine behind the scenes. Agenda-group work without the presence of JBPM: does it mean we can use the RF file for visualizing the agenda-groups as well? Could someone please shed some light on the differences between these constructs? Which one is the currently recommended approach (when?) for controlling rule execution flow? Thanks, Peter