1 files changed, 22 insertions, 0 deletions
diff --git a/extractor/features/is_source_singleton.h b/extractor/features/is_source_singleton.h
new file mode 100644
index 00000000..b8352d0e
--- /dev/null
+++ b/extractor/features/is_source_singleton.h
@@ -0,0 +1,22 @@
+#ifndef _IS_SOURCE_SINGLETON_H_
+#define _IS_SOURCE_SINGLETON_H_
+
+#include "feature.h"
+
+namespace extractor {
+namespace features {
+
+/**
+ * Boolean feature checking if the source phrase occurs only once in the data.
+ */
+class IsSourceSingleton : public Feature {
+ public:
+  double Score(const FeatureContext& context) const;
+
+  string GetName() const;
+};
+
+} // namespace features
+} // namespace extractor
+
+#endif