This article describes a small example of how the use of the Alloy modeling language can help in software development.
About the quality of software and tools
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newAuthCode clid sid = do
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void $ DB.deleteAllCodes clid sid
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open util/time // Time sig Operation // ... { delete : Time // ... - , insert : Time // ... - } { lt[delete,insert] // lt[first,delete] // // } run {some Operation} for 4 // // <= 4
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┌──────────────┬──────┬──────┐ │this/Operation│delete│insert│ ├──────────────┼──────┼──────┤ │Operation⁰ │Time¹ │Time³ │ ← Operation⁰ Time¹ ├──────────────┼──────┼──────┤ Time³ │Operation¹ │Time² │Time³ │ ← Operation¹ Time² └──────────────┴──────┴──────┘ Time³ ↑ !
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code <- run $ do
handleJust constraintViolation
(launchPG $ selectCodeForSession clid scope sid
(launchPG . pgWithTransaction $ newAuthCode clid scope sid)
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open util/time // Time sig Token {} // Token one sig DBState // {userToken : Token lone -> Time} // // (.. ) sig Operation { delete : Time , insert : Time , select : Time // select } { lt[first,delete] // // lt[delete,insert] // delete lte[insert,select] // select insert' no userToken.(insert.prev) // (.. => insert = select // ), // // (.. // 'INSERT RETURNING'). // // , select }
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fact Trace { // Trace all t : Time - first | { // , : some delete.t => no userToken.t // , some insert.t => some userToken.t // , no delete.t and no insert.t // , , => userToken.t = userToken.(t.prev) // } }
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assert selectIsGood { // , all s : Operation.select | // , select, some userToken.s // } check selectIsGood for 6 // , selectIsGood
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┌────────┬────────────┐ │DBState │userToken │ ├────────┼──────┬─────┤ │DBState⁰│Token²│Time³│ │ │ ├─────┤ ← Token² Time³ Time⁵ │ │ │Time⁵│ │ ├──────┼─────┤ │ │Token³│Time²│ ← Token³ Time². └────────┴──────┴─────┘ ↑ Time², Time³ Time⁵ , Time⁴ ! ┌──────────────┬──────┬──────┬──────┐ │Operation │delete│insert│select│ ├──────────────┼──────┼──────┼──────┤ │Operation⁰ │ TIME⁴│ Time⁵│ Time⁵│ ├──────────────┼──────┼──────┼──────┤ │Operation¹ │ Time¹│ Time³│ TIME⁴│ ← Time⁴ ├──────────────┼──────┼──────┼──────┤ select Operation¹! │Operation² │ Time¹│ Time²│ Time²│ └──────────────┴──────┴──────┴──────┘ ↑ ↑ ↑ ,
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- https://alloytools.org/ < —
- https://alloy.readthedocs.io/en/latest/ < —
- https://mitpress.mit.edu/books/software-abstractions < — Alloy, . , .
- https://alloytools.org/citations/case-studies.html < — Alloy . .
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