> For the complete documentation index, see [llms.txt](https://developer.collibra.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developer.collibra.com/workflows/designing-workflows/forms/form-expressions.md).

# Form expressions

Form expressions allow you to bind form components together to define a specific behavior. You can also use them for the majority of attributes and they are defined using double curly braces and a variable name, such as `{{form_expression}}`.

When you select any form component that is visible on the canvas, you are able to enter a value in the attribute bar on the right side of the canvas. The value option is mandatory. If you specify a form label or name right after adding the form component to the canvas, the value is added automatically for you.

You can then use variables with form expressions to build dependencies between form components.

{% hint style="info" %}
Arrays always evaluate to `true` even if the array is empty so the result of `{{checkBoxGroup ? 'yes' : 'no'}}` is *yes*. To build a condition on whether an array is empty, check the length, for example `{{checkBoxGroup.length > 0 ? 'yes' : 'no'}}` is *no* for an empty array.
{% endhint %}

Some of the options available in the attribute bar allow you to switch between simple and expression modes. For example, the **Required** option available in the attribute bar is by default in the normal mode. However, if you would like to mark a certain field as required based on a given condition you can click the lightning bolt icon next to the **Required** option label to switch to the expression mode.

<img src="/files/JuQ5LGT63LM31Zhucu5a" alt="" width="75%">


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