Let's finally model the various jurisdictions.
We would like to specify that certain properties of the traffic light system are required or prohibited in a given country or continent. 
To model specific choices of a jurisdiction we use clafer nesting (existence of a child clafer implies existence of the parent) as well as clafer and group cardinalities. 


```clafer
xor Jurisdiction
    Europe 
        UK ?    
    mux NorthAmerica
        USA
        Canada
    Australia
    NewZealand
```

First, we use `xor` to allow exactly one of `Europe`, `NorthAmerica`, `Australia`, and `NewZealand`. 
Since certain properties are specific to `UK` we can single it out as a child of `Europe`. 
This way, all properties relevant to `Europe` will also hold since an instance of `Europe` must exist for an instance of `UK` to exist. 
We use `mux` (meaning `0..1`) for `NorthAmerica` since we might choose a specific country (`USA` or `Canada`) or remain unspecific and only choose `NorthAmerica`.

How many choices for a jurisdiction does our model allow? 
Are they what you would expect? 

Is it possible to have an instance as follows? Why?

```
Jurisdiction
    Europe
        UK
    NorthAmerica
```

Let's use the ClaferConfigurator to generate all instances.

Why do you sometimes see two green ticks ![green tick](/tick.png) in a single column?

```{.clafer .config}
```

Close the Configurator and move to the page ![next](/next.png) [linking the jurisdiction and the system]().

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**Previous**
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1. [minimal traffic lights]()
2. [adding variability]()
3. [grouping choices]()