diff --git a/src/Witness.h b/src/Witness.h
index 5505068..d95b651 100644
--- a/src/Witness.h
+++ b/src/Witness.h
@@ -6,7 +6,7 @@ class WitnessPlan : public Plan
 public:
 	WitnessPlan (char const * const name, Plan * const input);
 	~WitnessPlan ();
-	Iterator * init () const;
+	Iterator * init () const override;
 private:
 	Plan * const _input;
 }; // class WitnessPlan
@@ -16,10 +16,18 @@ class WitnessIterator : public Iterator
 public:
 	WitnessIterator (WitnessPlan const * const plan);
 	~WitnessIterator ();
-	bool next (Row & row);
-	void free (Row & row);
+	bool next (Row & row) override;
+	void free (Row & row) override;
+	size_t getRowCount() const {return _rows;}
+	size_t getParity() const{return _parity;}
+	size_t getInversions() const {return _inversions;}
 private:
 	WitnessPlan const * const _plan;
 	Iterator * const _input;
 	RowCount _rows;
+	size_t _parity;   //store XOR of row values
+	size_t _inversions; //Number of inversions
+	Row _previousRow; //Last observed row
+	bool _hasPrevious; //If previous row is valid
+
 }; // class WitnessIterator