anchor.diff:  
   baseDecl
       : BASE IRI_REF -> ^(BASE IRI_REF)
  -    ;
  +    ; 
   
   prefixDecl
       : PREFIX PNAME_NS IRI_REF -> ^(PREFIX PNAME_NS IRI_REF)
  
positive.code:     ;
      
  groupGraphPatternSub
      : triplesBlock (graphPatternNotTriples DOT? triplesBlock?)* -> triplesBlock (graphPatternNotTriples triplesBlock?)*
      |(graphPatternNotTriples DOT? triplesBlock?)+ -> (graphPatternNotTriples triplesBlock?)+
      ;
  
  triplesBlock
  
negative.code:     ;
  
  subSelect
      : selectClause whereClause solutionModifier	-> ^(SUBSELECT selectClause whereClause* solutionModifier*)
      ;
      	
  selectClause
  