Yes, its making sure the verbs and activity types are actually valid adl defined verbs that I'm concerned about. I like the approach of making sure the final outcome is valid - maybe we can add to that here to say that if there isn't a verb or activity type defined by ADL, then the statement shouldn't be converted? We might also reassure the reader by stating that ADL has defined verbs and activity for all of those in the 0.9 spec.