Use of rdf:Statement to identify a class not allowed in OWL 2 #13

in iso19150/-2/2012/base.rdf rdf:Statement is used in a restriction on valueAssignment. However, rdf:Statement is not allowed to be used to identify a class in OWL 2. The relevant bits of the OWL specification are:

2.4 IRIs
IRIs with prefixes rdf:, rdfs:, xsd:, and owl: constitute the reserved vocabulary of OWL 2.

5.1 Classes
IRIs from the reserved vocabulary other than owl:Thing and owl:Nothing MUST NOT be used to identify classes in an OWL 2 DL ontology.

The definition for valueAssignment is: property that can be attached to any statement to support a link to the evidence for the value

This suggests that the functionality sought might be that of annotation axioms.
See 10.1 Annotations of Ontologies, Axioms, and other Annotations.