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https://github.com/salmans/rusty-razor

Razor is a tool for constructing finite models for first-order theories
https://github.com/salmans/rusty-razor

chase geometric-logic model-finding rust-lang theorem-proving

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Razor is a tool for constructing finite models for first-order theories

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# rusty-razor



Rusty Razor is a tool for constructing finite models for first-order theories. The model-finding algorithm is inspired

by [the chase](https://en.wikipedia.org/wiki/Chase_(algorithm)) for database systems. Given a first-order theory,

Razor constructs a set of *homomorphically minimal* models for the theory.



Check out Razor's [documentation](https://salmans.github.io/rusty-razor/intro.html) for more information about the project and introductory examples.



## Build



rusty-razor is written in Rust, so you will need [Rust](https://www.rust-lang.org) 1.48.0 or newer to compile it.

To build rusty-razor:



```

git clone https://github.com/salmans/rusty-razor.git

cd rusty-razor

cargo build --release

```



This puts rusty-razor's executable in `/target/release`.



## Run



### `solve`



Use the `solve` command to find models for a theory written in an `` file:



```

razor solve -i 

```



The `--count` parameter limits the number of models to construct:



```

razor solve -i  --count 

```



#### Bounded Model-Finding



Unlike conventional model-finders such as [Alloy](http://alloytools.org), Razor doesn't require the user to provide a

bound on the size of the models that it constructs. However, Razor may never terminate when running on theories with

non-finite models -- it can be shown that a run of Razor on an unsatisfiable theory (i.e., a theory with no models)

is guaranteed to terminate (although it might take a very very long time).This is a direct consequence of

semi-decidability of first-order logic.



To guarantee termination, limit the size of the resulting models by the number of their elements using the `--bound`

option with a value for the `domain` parameter:



```

razor solve -i  --bound domain=

```



#### Model-Finding Scheduler



Use the `--scheduler` option to choose how Razor processes search branches. The `fifo` scheduler (the default scheduler)

schedules new branches last and is a more suitable option for processing theories with few small satisfying models.

The `lifo` scheduler schedules new branches first, and is more suitable for processing theories with many large models.



```

razor solve -i  --scheduler 

```



## Toy Example



Consider the following example:



```

// All cats love all toys:

forall c, t . (Cat(c) and Toy(t) implies Loves(c, t));



// All squishies are toys:

forall s . (Squishy(s) implies Toy(s));



Cat('duchess);   // Duchess is a cat

Squishy('ducky); // Ducky is a squishy

```



You can download the example file [here](https://github.com/salmans/rusty-razor/blob/master/theories/examples/toy.raz) and run the `razor` command-line tool on it:



```

razor solve -i theories/examples/toy.raz

```



Razor returns only one model with `e#0` and `e#1` as elements that denote `'duchess` and

`'ducky` respectively. The facts `Cat(e#0)`, `Squishy(e#1)`, and `Toy(e#1)` in the model

are directly forced by the last two formula in the input theory. The fact `Loves(e#0, e#1)`

is deduced by Razor:



```

Domain: e#0, e#1



Elements: 'duchess -> e#0, 'ducky -> e#1



Facts: Cat(e#0), Loves(e#0, e#1), Squishy(e#1), Toy(e#1)

```



Razor's documentation describes the [syntax](https://salmans.github.io/rusty-razor/syntax.html)

of Razor's input and contains more [examples](https://salmans.github.io/rusty-razor/example.html).