@ruiting, thanks for the explanation. At the moment, to-do-rules 1-5 are defined in https://github.com/opencog/relex/blob/master/data/relex2logic-rules.txt, but there are only helper functions for to-do-rules 1-3 in https://github.com/opencog/opencog/blob/master/opencog/nlp/scm/relex-to-logic.scm.