anchor.diff:      ;
   
   groupOrUnionGraphPattern
  -    : groupGraphPattern (UNION groupGraphPattern)* -> groupGraphPattern ^(UNION groupGraphPattern*)?
  +    : groupGraphPattern (UNION ^groupGraphPattern)*
       ;
   
   filter
  
positive.code:     ;
  
  triplesSameSubjectPath
      : varOrTerm propertyListNotEmptyPath 
      | triplesNode propertyListPath
      ;
    
  propertyListNotEmptyPath
  
negative.code: COLLECTION;
  BLANKNODEPROPERTYLIST;
  OBJECTLIST;
  TRIPLE;
  NOTEXISTS;
  CONDITIONAL_OR_EXPRESSION;
  CONDITIONAL_AND_EXPRESSION;
  