anchor.diff:      ;
   
   graphGraphPattern
  -    : GRAPH varOrIRIref groupGraphPattern
  +    : GRAPH varOrIRI groupGraphPattern
       ;
   
   serviceGraphPattern
  -    : SERVICE SILENT? varOrIRIref groupGraphPattern
  +    : SERVICE SILENT? varOrIRI groupGraphPattern
       ;
       
   bind
  
positive.code:     ;
  
  describeQuery
      : DESCRIBE (varOrIRIref+ | ASTERISK) datasetClause* whereClause? solutionModifier
      ;
  
  askQuery
  
negative.code:     : var | graphTerm
      ;
  
  varOrIRI
      : var | iri
      ;
  
  