SICStus Prolog is a workhorse in the transport and logistics industries, running systems that handle a third of all airline tickets, and helping railways to operate their trains better.
“Most people probably have used SICStus Prolog without knowing it,” says Mats Carlsson, its lead developer. “One of our customers runs a flight booking system on SICStus which handles nearly a third of all airline tickets in the world.”
https://web.archive.org/web/20190203010151/https://www.sics....
The new homepage doesn't say anything about flight bookings and I can't find anything about it in the "Customers" page either:
https://sicstus.sics.se/customers.html
I have a sneaking suspicion that might mean the customer replaced Prolog with something else, possibly some kind of machine learning :P
They are still around if you want to get in touch.
I recall two key things from his presentation of his final product.
First, he claimed he'd quoted a half the cost/time of a COBOL-based, and a quarter of a C-based, competing tenders -- and that he'd met his deadlines.
Second, the UI was just beautiful - for both aesthetics and performance.
I didn't have much experience in enterprisey software at the time, but what little I had seen was archetypal terminal-style, monochrome, sluggish, far from user-friendly etc. I have some (no doubt unreliable) memories of this thing looking like a 'modern' (say Amiga) GUI app.
Another item in that large category of 'I wish they'd drop these things into the public domain once they retired it from production' as it would probably still make a great demo (though most free Prolog implementations these days wouldn't support (m)any of the pretty Turbo extensions, I'm sure).