diff --git a/sbg/dto/interval_dto.cpp b/sbg/dto/interval_dto.cpp
index 4532553..84baf31 100644
--- a/sbg/dto/interval_dto.cpp
+++ b/sbg/dto/interval_dto.cpp
@@ -30,6 +30,9 @@ IntervalDTO::IntervalDTO(const NAT &begin, const NAT &step, const NAT &end)
 {
 }
 
+// Set functions ---------------------------------------------------------------
+bool IntervalDTO::isEmpty() const { return end_ < begin_; }
+
 // Operators -------------------------------------------------------------------
 std::ostream &operator<<(std::ostream &out, const IntervalDTO &i) 
 {
diff --git a/sbg/dto/interval_dto.hpp b/sbg/dto/interval_dto.hpp
index aebbb94..0d70ada 100644
--- a/sbg/dto/interval_dto.hpp
+++ b/sbg/dto/interval_dto.hpp
@@ -44,6 +44,11 @@ struct IntervalDTO {
   IntervalDTO(const NAT &x);
   IntervalDTO(const NAT &begin, const NAT &step, const NAT &end);
 
+  /**
+   * @brief Traditional set operations.
+   */
+  bool isEmpty() const;
+
   private:
   NAT begin_;
   NAT step_;