eliminated separate stamp -- NameSpace.define/merge etc. ensure uniqueness already;
fully authentic merge;
(benchmark Isabelle
:extrasorts ( T1)
:extrapreds (
(up_1)
(up_2)
(up_3)
(up_4)
)
:assumption (or (and up_1 up_2) (and up_3 up_4))
:assumption (not (or (and up_1 up_2) (and up_3 up_4)))
:formula true
)