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