position_stmt : POSITION_KEYWORD string stmtend;
bit_stmt : BIT_KEYWORD string (SEMICOLON | (LEFT_BRACE (identifier_stmt |position_stmt | status_stmt | description_stmt | reference_stmt )* RIGHT_BRACE));
bits_specification : bit_stmt (bit_stmt | identifier_stmt)*;
-union_specification : type_stmt (identifier_stmt | type_stmt )+;
+union_specification : type_stmt (identifier_stmt | type_stmt )*;
identityref_specification : base_stmt ;
instance_identifier_specification : (require_instance_stmt )?;
require_instance_arg :string; // TRUE_KEYWORD | FALSE_KEYWORD;