# GuessTheSpec #2

**URL:** <https://alloytools.discourse.group/t/guessthespec-2/110>\
**Category:** Uncategorized\
**Created:** [September 25, 2020, 11:03am UTC](https://alloytools.discourse.group/t/guessthespec-2/110 "2020-09-25T11:03:20Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![alcino](https://yyz2.discourse-cdn.com/free1/user_avatar/alloytools.discourse.group/alcino/32/25_2.png) [@alcino](https://alloytools.discourse.group/u/alcino)\
**Post date:** [September 25, 2020, 11:03am UTC](https://alloytools.discourse.group/t/guessthespec-2/110/1 "2020-09-25T11:03:20Z")

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Hi,

Here is a new challenge for this weekend: [http://alloy4fun.inesctec.pt/rDMR6CPz4eDCPHHzW](http://alloy4fun.inesctec.pt/rDMR6CPz4eDCPHHzW)

Just to recall how this works:

- You should write your candidate specification (one or more properties) inside predicate `spec` . You can actually change the rest of the model, but that is cheating 🙂
- If you press the execute button on the right you will either get a “No counter examples found” message, meaning you solved the challenge, or you will get a counter-example instance (already “beautified” with a minimal theme)
- Notice that the counter-example can either be an instance that holds in your (incorrect) spec but not in the correct one, or the other way around, so think carefully about which one is the case
- You can move the atoms around and ask for more counter-examples

And a tip that can help: if you write a false formula inside predicate `spec`, for example `some none`, you will only see instances that satisfy the correct specification.

Good luck,  
Alcino

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**Author:** ![grayswandyr](https://yyz2.discourse-cdn.com/free1/user_avatar/alloytools.discourse.group/grayswandyr/32/17_2.png) [@grayswandyr](https://alloytools.discourse.group/u/grayswandyr)\
**Post date:** [October 6, 2020, 10:02am UTC](https://alloytools.discourse.group/t/guessthespec-2/110/2 "2020-10-06T10:02:15Z")

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Funny 🙂

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**Author:** ![grayswandyr](https://yyz2.discourse-cdn.com/free1/user_avatar/alloytools.discourse.group/grayswandyr/32/17_2.png) [@grayswandyr](https://alloytools.discourse.group/u/grayswandyr)\
**Post date:** [October 6, 2020, 3:55pm UTC](https://alloytools.discourse.group/t/guessthespec-2/110/3 "2020-10-06T15:55:16Z")

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A nice feature would be that as gratification, once you succeed, you get to see the hidden spec, to compare with your own specification style.

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**Author:** ![alcino](https://yyz2.discourse-cdn.com/free1/user_avatar/alloytools.discourse.group/alcino/32/25_2.png) [@alcino](https://alloytools.discourse.group/u/alcino)\
**Post date:** [October 6, 2020, 6:24pm UTC](https://alloytools.discourse.group/t/guessthespec-2/110/4 "2020-10-06T18:24:37Z")

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Eventually I will share all the different correct specs that were submitted.