anchor.diff:      : var | graphTerm
       ;
   
  -varOrIRIref
  +varOrIRI
       : var | iri
       ;
   
  
positive.code:     ;
  
  describeQuery
      : DESCRIBE (varOrIRIref+ | ASTERISK) datasetClause* whereClause? solutionModifier
      ;
  
  askQuery
  
negative.code:     ;
  
  verb
      : varOrIRI | A
      ;    
  
  objectList
  