TLA+ is a specific kind of formal verification framework for software. The overall idea is that you can "prove" that some software works, rather than the typical "seems like it works" we aim for.
But under the covers, all formal verification schemes are (imho) best viewed as "very fancy testing". There are a few kinds of this fancy testing. TLA+ is the kind that can auto-generate all the relevant test cases for your code (there's more to it than that, but this definition works for now). So now instead of "I wrote a bunch of test cases, all that I could think of, and they pass" you have "I used TLA+ so I know I'm exercising all the possible test cases and they pass".
Here's the problem though: to achieve that trick, you have to write your code in a special language (TLA+). It isn't a tool that can be just pointed at regular production code.
So what you get to "prove" is a translation of your actual code into TLA+ code. It may be possible to auto-translate one to the other (I asked the original author if they did that, but no reply yet). Usually it's a manual process.
Therefore you have "proof" but not quite as you know it, because you proved something different than what runs. But still more useful than a wet finger raised into the wind.
For this reason it's typically only used on narrow risky pieces of code (quorum voting is the canonical use case).
This makes sense to me but if I continue with the "fancy testing" analogy it seems like there is no accounting for interactions beyond the system itself: it has perfect unit and integration testing but only for a myopic amount of global state.
I am curious about the limits of what one can expect this language to solve and therefore the types of programs/domains to which it is more/less suited. Why is determining quorum the canonical use case?
Have you ever been to Europe?? Things they are building: proper trains; proper roads; proper particle accelerators; proper airliners; proper bread; proper cars; the AI that the USA thinks is so amazing; ARM CPUs; ...
And speaking of "a less prosperous society" -- have you been to most of the USA recently? Doesn't look very prosperous to me vs most of Europe.
Yes but anyone who posts something about "loads of innocent people arrested for just voicing their opinion (man)" is implicitly disingenuous. I say that because the first time I heard someone say this (a friend who lives in the UK no less) I thought "that doesn't seem right" and so did a few minutes of Google searching. And of course it isn't right. People have been arrested for being threatening a.holes which seems perfectly fine. For comparison here in the middle of the US we have a lady in town who liked to send death threats (via mail) to the town manager, based on his chosen policies for street crossings, or something. Well she was arrested and put in jail for a while. She said she really didn't mean it, it was all a joke. Still in jail.
I've seen this headline floating in my feed for a while and assumed it was about some place called Portobello in North Carolina or similar. But having discovered it's about the real Portobello...down the rabbit hole...
At first I thought the bell chime controller was a hobby project. Long ago there were many electronics firms in the Edinburgh area so someone who worked as an EE could easily have knocked up the controller using "appropriated" parts from work. But the soldering is not quite right. It's too good for a total beginner, but not good enough for a professional. Also the single chip I think implies an MCU of some sort, so it's not going to be more than about 30 years old. A date code from the chip would be nice.
Then I realized that "box to control church bells" is probably a thing and a quick Google search dragged up this: https://www.electronics-lab.com/project/church-bell-controll... note that the PCB in the 5th picture bears a more than passing resemblance to the one at Porty.
Fun fact: my Dad's mother's family ran a shop on the High Street in the late 1800's. The building is still there and is on the next block down the road from the police station.
I'm sure people laughed at Oppenheimer when he said perhaps we don't make this atomic bomb thing. They said "of course he's saying that because he knows it won't work".
Local people know where they are because once upon a time a D8 drove through pulling a big orange spool of fiber conduit and passers by chatted about how another fiber was going in. Also around here the contractors seeded the disturbed ground with a wildflower mix (presumably to discourage weeds) so you can also look for straps of wildflowers.
And of course there are marker posts that say "buried fiber optic cable do not dig".
Once you get out farther from civilization these signs become less common and there are more situations where they can get removed.
Most cheap hired labor doesn't realize you shouldn't dig up the market posts and throw them in the dumpster on construction sites. Add a little bit of rain and suddenly the contractor showing up with an excavator that was told everything was properly marked, and can see markings in other places but not where they are digging, and disaster occurs.
Also soils aren't static, I've been on sites where the midpoint of a buried telecommunications cable had drifted over 8 feet from where the markers were a few hundred yards apart. Just looking at the markers and assuming a straight line isn't a safe bet. Looking at the fence rows to the left and right of the cable and you could see a matching bow in the fence rows.
I see you've never dug into a cable way out of range where the utility thought it was. You've definitely never been on a project where the utility was there with you wondering how the wire they marked many many feet away out of the hand dig area was actually where you're digging.
I was on such a project once back when PRI was still a hot ticket. Part of the project evolved to mean that we needed to construct a small radio tower, and a part of that meant finding a spot where we wouldn't dig up anything important.
Reps from the local telco showed up to one of the meetings to tell everyone that they didn't know where their copper lines were buried and that they were unsuccessful at locating them outside at all. They knew where both ends were but the middle was a mystery to them.
This statement made the architect's face contort into strange shapes. I joked that they call 811; some people thought that was rather hilarious, others much less so.
Anyway, the building wasn't in service yet and the telco said they'd fix it if we managed to naff them up, so away we dug. No telco cabling was damaged in this process. (We did dig up some plastic drainage tile but that was a simple farm store fix.)
TLA+ is a specific kind of formal verification framework for software. The overall idea is that you can "prove" that some software works, rather than the typical "seems like it works" we aim for.
But under the covers, all formal verification schemes are (imho) best viewed as "very fancy testing". There are a few kinds of this fancy testing. TLA+ is the kind that can auto-generate all the relevant test cases for your code (there's more to it than that, but this definition works for now). So now instead of "I wrote a bunch of test cases, all that I could think of, and they pass" you have "I used TLA+ so I know I'm exercising all the possible test cases and they pass".
Here's the problem though: to achieve that trick, you have to write your code in a special language (TLA+). It isn't a tool that can be just pointed at regular production code.
So what you get to "prove" is a translation of your actual code into TLA+ code. It may be possible to auto-translate one to the other (I asked the original author if they did that, but no reply yet). Usually it's a manual process. Therefore you have "proof" but not quite as you know it, because you proved something different than what runs. But still more useful than a wet finger raised into the wind.
For this reason it's typically only used on narrow risky pieces of code (quorum voting is the canonical use case).
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