For example one can define a Class Examination which is a Subclass of something which has at least two Professors as examiners. In OWL it is stated by saying that Examination is aClass which is a Subclass of a, owl:Restriction. The Restriction is on the PropertyhasExaminer. Then one does the number restriction but as Qualified number restriction, which is here are lower bound, i.e. at least two Examiners. So one says owl:minQualifiedCardinality should be at least 2 as a `nonNegativeInteger from the XML Schema Definition. Because it is aQualified Number Restriction one has to specify the class on which it applies as a Range for that Property, which is here owl:onClass Professor.
So one can define a Qualified Number Restriction to an exact number or an lower/upper bound and on a specific Range. This allows to define a lower, upper or exact value that has to be fulfilled.
OWL enables Class Constructors with number restrictions on properties connected with a Range constraint
E.g. Examination ⊑ ≥2 hasExaminer.Professor
:Examination a owl:Class;
a owl:Restriction ;
owl:onProperty :hasExaminer ;
owl:onClass :Professor ] .