This mandatory block enforces the rule that its containing members and groups must have at least one member selected before the form can successfully be submitted.

 

There are, however, a subtle differences between using this widget or using the button assistant and checking the "Mandatory" box in the creation wizard for the assistant:

 

•The Mandatory Block by default leaves all its contained buttons or checkboxes unchecked or without value. If end users try to submit the form with all these boxes unselected or unfilled, the error message for the block is displayed and all the contained elements get red outlines.
 

•Checking the "Mandatory" box of the button assistant wizard means that at least one of the buttons (the first by default) is selected at form initialization and there is no way to go to an all-unselected condition.
 

•Several checkbox or buttons blocks can be contained in the mandatory block, all of them unchecked at initialization, and yet only one button of one group must be selected before submission and all the other buttons in the other groups can remain unchecked.