Nothing-but gives restriction on range of a property (role) or data type of a data property. It is so called universal role restriction.


Those examples show how to restrict range of a role or data type of a data property.

Example: If something has a wife, then it must be a person. Range of is-a-wife-of property is a person class
Every-single-thing is-a-wife-of nothing-but persons.
Example: Names are words. The name property can be only of type string.
Every-single-thing has-name nothing-but (some string value).