---
title: Modeling Variability 5
categories: demo
toc: false
...

Adding a constraint: Adaptive cruise control (`ACC`) requires forward collision alert (`FCA`).

```clafer
abstract Car
    ABS ?
    xor Transmission
        Automatic
        Manual
    `FCA ?
    `CC ?
    [ ACC => FCA ]
```

The Forward Collision Alert (FCA) subsystem.

```clafer
abstract FCA
    xor Sensor
        Radar
        Lidar
    xor Alert
        Haptic
        Audible
```

The Cruise Control (CC) subsystem.

```clafer
abstract CC
    switch
        backlight ?
    ACC ?
```

[Modeling Variability 6]()