diff --git a/src/utils/tstring.hpp b/src/utils/tstring.hpp
index 5b17d98..8f9701a 100644
--- a/src/utils/tstring.hpp
+++ b/src/utils/tstring.hpp
@@ -112,5 +112,21 @@
     }
 };
 
+struct CollectionTimeScope
+{
+    static std::string str()
+    {
+        return "collectionTimeScope";
+    }
+};
+
+struct CollectionDuration
+{
+    static std::string str()
+    {
+        return "collectionDuration";
+    }
+};
+
 } // namespace tstring
 } // namespace utils