what makes an OWL class anonymous?

Question

I am reading a tutorial that says that this is an anonymous OWL class:

<owl:Class rdf:ID="Reptile"> 
       <rdfs:subClassOf rdf:resource="#Animal”/> 
       <rdfs:subClassOf rdf:resource="#OxygenUser”/> 
</owl :Class>

I know what an anonymous class is in Java. What makes this class anonymous in OWL? Is it anonymous because it does not have an RDFS:label statement like this: <rdfs:label>Reptile</rdfs:label> ?

Answer 1

OWL anonymous classes are classes without a name/identifier (URI). Usually it's an OWL class expression such as eats some Grass or Male and Female . You use such expression in combination with named classes to create axioms.

Example of equivalent classes axioms using both named an anonymous classes (comments are shown by the # symbol):

# Named class (got a dereferencable URI)
Class: <http://www.example.org/Man>

# Named Class
Class: <http://www.example.org/Woman>

# Named class
Class: <http://www.example.org/Human>

    # The named class Human is equivalent 
    # to the anonymous class (class expression) Man or Woman
    EquivalentTo: <http://www.example.org/Man> or <http://www.example.org/Woman>

Answer 2

Do you have a source URL for the tutorial? The example you quote does not contain any anonymous classes, so if that's a direct quote from the tutorial, it's giving out wrong information.