Definition hist_incl (h : hist_part) l := forall t e, h t = Some e -> nth_error l t = Some e.
Definition hist_list (h : hist_part) l := forall t e, h t = Some e <-> nth_error l t = Some e.

Lemma hist_next : forall h l (Hlist : hist_list h l), h (length l) = None.
Definition ghost_hist_ref sh (h r : hist_part) g :=
own(RA := ref_PCM map_disj_PCM) g (Some (sh, h), Some r) NoneP.