# File lib/tapkit/control/qualifier.rb, line 366
                def validate( description )
                        property_keys = description.all_property_keys

                        qualifier_keys.each do |keypath|
                                key = keypath.split('.').first
                                unless property_keys.include? key then
                                        raise UnknownKeyError, "Qualifier found an unknown key '#{key}'"
                                end
                        end
                end