theorem instProcessBoundaryAtToParent
theorem instProcessBoundaryAtToParent: ∀ (x t : Type) [ProcessBoundary.At x t], Occurrent.At x t
theorem instProcessBoundaryAtToParent
theorem instProcessBoundaryAtToParent: ∀ (x t : Type) [ProcessBoundary.At x t], Occurrent.At x t