[lmm]

But you can't do interaction between the two ends of a HTTP request. The caller makes an inert request, whatever processing happens downstream of that might as well be offline because it's not and can never be interactive within a single transaction.

[Tainnor]

Now you're shifting the goalposts. You started out by claiming that web apps can't be transactional, now you've switched to saying they can't be transactional if they're "interactive" (by which you presumably mean transactions that span multiple HTTP requests).

Of course, that's a very particular demand, one that doesn't necessarily apply to many applications.

And even then, depending on the use case, there are relatively straightforward ways of implementing that too: For example, if you build up all the data on the client (potentially by querying the server, with some of the partial data, for the next form page, or whatever) and submit it all in one single final request.