This is a great summary and hits all the points I've been wondering about spreadsheets, with plenty more. I didn't know about EUSPRIG, thanks for that link!

Also, I strongly recommend looking at Coda if you haven't already. I've seen so many new spreadsheet tools, but Coda seems (to me, at least) way ahead in terms of both features and flexibility: • Much better formula language than Excel • Lovely UI for writing & debugging formulae • Tons of ways to build reactive documents and apps on top of the data • All the right kinds of product polish (to these eyes, anyway) The main downside: closed source, alas.

There's another problem with Coda that seems inherent to the model of keeping data and computation together: forking is easy (copy the document) but there's no easy way to merge improvements from forks back into the original. It takes careful manual work to separate the data changes from the logic changes, unlike traditional code where the two are already separate. What makes them bleed together is the third circle in your Venn diagram: Presentation. When I add text in a Coda document, I might consider it Data (to be ignored, or swapped with a placeholder) or UI (to be treated as part of the App Logic). Coda, at present, can't tell the difference. I mention it here because the need to fork and then merge logic back to the original is likely to come up pretty quicky.

> It takes careful manual work to separate the data changes from the logic changes, unlike traditional code where the two are already separate. One software analogue I’d apply here are creating different environments of an application – for ex. a staging/QA environment and a production environment for a web app. Keeping them in sync is made possible by versioning schema changes (of the code and the database) separately. This does imply making the separation between schema and data explicit (i.e presentation and everything else). Many more things depend on this separation. The hard bit is to do it in a way that requires little upfront commitment from users.

(And kudos to Rich Harris for this line in the above blog post: "_Like every other framework, we've come to the realisation that Knockout was right all along."_)

Oh, and I forgot about Solid, which seems to come up far more often in random web dev discussions than I would expect.