This is a datatype.
Please note: datatypes are not (yet) copied from the DBpedia Mappings Wiki to the DBpedia ontology. They are hard-coded in OntologyDatatypes.scala and were added to the wiki for reference. Adding a datatype in the wiki does not change the ontology and leads to an error messsage for properties that use such a datatype.
See all datatypes known to the DBpedia Extraction Framework.