A RDF instance can have multiple class inheritances, but today we don’t tolerate it. A class can have multiple parents but an instance can have only one class.
This makes a lack in our RDF implementation. We should fill it.
To keep the efficiency of the management of the graph database and because we want to keep it simple (as possible), we will implement the multi heritance by introducing virtual classes.
This modelization brings advantages at the implementation. The impact on the code is very low. A little patch that create/or reference anonymous classes.