anchor.diff:      | ^(IRI expression)
       | ^(URI expression)
       | ^(BNODE expression)
  +    | BNODE
       | RAND
       | ^(ABS expression)
       | ^(CEIL expression)
  
positive.code:     ;   
      
  load 	  
      : ^(LOAD SILENT* iriRef graphRef*)
      ;
      
  clear
  
negative.code:     ;
      
  iriRefOrFunction
      : ^(FUNCTION f=iriRef ^(ARG_LIST (a=argList)))
      | ^(FUNCTION f=iriRef)
      ;
  
  rdfLiteral
  