It's not just tracability and security that's the issue, though. It's an issue of reproducibility. When I give you a notebook, how do you 'run' it to verify my

It's not just tracability and security that's the issue, though. It's an issue of reproducibility. When I give you a notebook, how do you 'run' it to verify my calculations? You can't just press "run", because I might have executed the cells out of order, or deleted cells which later cells depended on. Version control doesn't solve this problem. Good practice might solve it, but it turns out that researchers are stunningly bad at following a strict top-to-bottom execution of notebooks. And who can blame them? The non-linearity of notebooks is one of their features. But when it comes to reproducibility and just the basic mechanics of sharing code, we definitely need a better solution.