code: private InternalQName getNodeTypeName(Node config) throws IllegalNameException, RepositoryException
     {
        String ntString = config.getAttributes().getNamedItem("primaryType").getNodeValue();
        return resolver.parseJCRName(ntString).getInternalName();
     }
docs: Reads the node type of the root node of the indexing aggregate.
  
  @param config the configuration.
  @return the name of the node type.
  @throws IllegalNameException   if the node type name contains illegal
  characters.
  @throws RepositoryException