===good============ Acme.preferred_customer <- Coyote
YAP query succeed
prover success!!
credentials needed :
 pAcme.preferred_customer  <- pCoyote 
  
===good=============== Acme.buy_rockets <- Coyote
YAP query succeed
prover success!!
credentials needed :
 pAcme.buy_rockets  <- pAcme.preferred_customer 
 pAcme.preferred_customer  <- pCoyote 
  
===bad=============== Acme.buy_rockets <- Acme.preferred_customer
fail, a.o <- b.o and a.r <- a.r query is not implemented yet !!!
  
===bad=============== Coyote.friend <- Acme
YAP query failed
prover failed!!