...final principal set...
(pAcme,keyid,y) 
(pAlice,keyid,y) 
(pBob,keyid,y) 
(pDave,keyid,y) 
(pGlobotron,keyid,y) 

...final policy attribute set...
pAcme.experiment_create <- pAcme.partner.experiment_create
pAcme.partner <- pGlobotron
pAlice.power_user <- pBob
pDave.power_user <- pBob
pGlobotron.admin <- pAlice
pGlobotron.admin <- pDave
pAcme.experiment_create <- pGlobotron.admin.power_user

===good=============== Acme.experiment_create <- Bob
YAP query succeed
pAcme.experiment_create <- pGlobotron.admin.power_user
pGlobotron.admin <- pAlice
pAlice.power_user <- pBob

next proof:
pAcme.experiment_create <- pGlobotron.admin.power_user
pGlobotron.admin <- pDave
pDave.power_user <- pBob

next proof:
no more..