PrF UG slots value type boolean
From Protege Wiki
The Boolean Value Type
A Boolean slot holds a logical Boolean value; that is, a value that is either true or false. To set the value type of a slot to Boolean:
Select Boolean from the Value Type menu.
The Name of the slot will be used as a label for the checkbox; make sure this is what you want.
When an instance is created for a class with a Boolean slot, the instance entry field corresponding to the slot is a Boolean field and is displayed as a checkbox:
For example, the Personals_Ad class contains the Boolean slot Urgent; the Silly instance of Personals_Ad is not Urgent, while the M137 instance is.