[HN Gopher] Breaking the limits of TLA+ model checking
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Breaking the limits of TLA+ model checking
 
Author : todsacerdoti
Score  : 93 points
Date   : 2023-04-17 15:11 UTC (7 hours ago)
 
web link (www.hillelwayne.com)
w3m dump (www.hillelwayne.com)
 
| dwohnitmok wrote:
| RE the OP's work to add probability-weighted state transitions,
| more generally TLA+ doesn't have the ability to talk about state
| transitions (i.e. actions in TLA+) themselves in a first class
| way, which makes certain invariants very annoying or impossible
| to state (e.g. we will converge after no more than 5 steps). I
| wonder if there's a clean way to extend TLA+ to cover these
| cases. Admittedly they don't come up that frequently.
 
  | nano_o wrote:
  | In your example, you can just add a variable that is
  | incremented at every step and then use it to state your
  | invariant that convergence must happen within 5 steps.
  | 
  | Sometimes you can encode properties that might initially seem
  | hard to state in TLA+ in a similar way. Lamport has a recent
  | paper explaining how to do that for hyperproperties such as
  | information-flow security:
  | http://lamport.azurewebsites.net/pubs/pubs.html?from=https:/...
 
| Nezteb wrote:
| The repo: https://github.com/hwayne/tla-graphing-demo
 
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