...final principal set...
(pAcme,keyid,y) 
(pCoyote,keyid,y) 

...final policy attribute set...
pAcme.buy_rockets <- pAcme.preferred_customer
pAcme.preferred_customer <- pCoyote

===good============ Acme.preferred_customer <- Coyote
YAP query succeed
pAcme.preferred_customer <- pCoyote

===good============ Acme.buy_rockets <- Coyote
YAP query succeed
pAcme.buy_rockets <- pAcme.preferred_customer
pAcme.preferred_customer <- pCoyote

===bad=============== Coyote.friend <- Acme
YAP query failed

===bad=============== Acme.buy_rockets <- Acme.preferred_customer
fail, a.o <- b.o and a.r <- a.r query is not implemented yet !!!