ALF - Mandatory field use

Question
I would like to better understand how mandatory fields are used? The documentation says that they are used only with 'custom event handlers' and except that I do not see anything in the knowledge base. Are there examples of using mandatory fields?

Answer
Mandatory fields are not a custom code specific function. In DesignTool, 'Mandatory' is set to to make a field mandatory. The user will be notified in any of the ALF clients if no data has been entered into these mandatory fields. It will stay in the ALF client until the needed data has been submitted or edited on the client. You can use the 'Mandatory' function on any field you feel should be mandatory. 

There are no rules how many you can have or what field to add it to, except for checkboxes that are included in a group. You can't have a checkbox mandatory if you intend to use it in a checkbox group - you can set the checkbox group to be mandatory. We normally see this on product ID's, but also on fields such as First and Last name. As for checkbox groups along with mandatory fields: 
You will get the value of the checkbox itself but loose the group value and as a result, in the XML file, it will look as if you checked the correct checkboxes but the viewer will not show correct values as it only shows the group value. All the other fields will work as they are supposed to and the same applies to the checkboxes outside of groups.