diff --git a/src/ast_values.hpp b/src/ast_values.hpp
index 44e98af..b2f2c3a 100644
--- a/src/ast_values.hpp
+++ b/src/ast_values.hpp
@@ -38,9 +38,23 @@
     std::string m_value;
 };
 
+enum class SpecialValue {
+    List,
+    Container,
+    PresenceContainer
+};
+
+struct special_ {
+    bool operator==(const special_& b) const;
+    SpecialValue m_value;
+};
+
+std::string specialValueToString(const special_& value);
+
 using leaf_data_ = boost::variant<enum_,
                                   binary_,
                                   identityRef_,
+                                  special_,
                                   double,
                                   bool,
                                   int8_t,