An example is given by the following graph Gex:a a ex:Cand basic graph pattern BGP?x a [ a owl:Class ; owl:unionOf ( ex:C ex:D ) ]The graph G states that ex:a has type ex:C, while the BGP asks for instances of the complex class denoting the union of ex:C and ex:D. One might expect that a solution mapping ?? that maps ?x to ex:a is a solution, but this is not the case under the OWL 2 RDF-Based Sema