How assert data property for classes in Protege?

I want to model Person class which takes data property givenName of type xsd:string. How to specify length restriction of this property (say maxLength=50) that is applicable only for Person class? For example, I want to allow other classes to use the same property and choose different value for restriction.

First of all, OWL is not a constraint language. It is intended rather to define classes based on restrictions, than to set up restrictions for classes.

However, one can define anonymous “restriction-based” class and declare another class to be a subclass of this anonymous class.

In the Manchester syntax, you can write something like this:

Class: Person
    SubClassOf: givenName only xsd:string[maxLength 5]

In the Functional syntax:

SubClassOf(
    :Person
    DataAllValuesFrom(
        :givenName
        DatatypeRestriction(
            xsd:string
            xsd:maxLength "5"^^xsd:string
        )
    )
)

In the Turtle syntax:

:Person rdfs:subClassOf
    [ rdf:type owl:Restriction ;
      owl:onProperty :givenName ;
      owl:allValuesFrom
      [ rdf:type rdfs:Datatype ;
        owl:onDatatype xsd:string ;
        owl:withRestrictions ( [ xsd:maxLength "5"^^xsd:string ] )
      ]
    ] .

The image below is the "Class description" view in Protégé:

Now suppose you declare that

Individual: He
    Types: Person
    Facts: givenName  "Alexander"^^xsd:string

Then reasoner (e.g. HermiT) have to say that your ontology is inconsistent: