diff --git a/src/include/ranges/value_range.h b/orig/include/ranges/value_range.h
similarity index 100%
rename from src/include/ranges/value_range.h
rename to orig/include/ranges/value_range.h
diff --git a/src/include/base/types.h b/src/include/base/types.h
index 3debdc4..9c5e93d 100644
--- a/src/include/base/types.h
+++ b/src/include/base/types.h
@@ -64,6 +64,12 @@ namespace CNORXZ
 
     template <class I, typename MetaType>
     using IndexPtr = Sptr<IndexInterface<I,MetaType>>;
+
+    // definition: ranges/nrange.h
+    class NRange; // null-range (range over none)
+
+    // definition: ranges/nrange.h
+    class NIndex;
     
     // definition: ranges/urange.h
     template <typename Meta>
diff --git a/src/include/ranges/range_types/classic_range.h b/src/include/ranges/crange.h
similarity index 100%
rename from src/include/ranges/range_types/classic_range.h
rename to src/include/ranges/crange.h
diff --git a/src/include/ranges/multi_range.h b/src/include/ranges/mrange.h
similarity index 100%
rename from src/include/ranges/multi_range.h
rename to src/include/ranges/mrange.h
diff --git a/src/include/ranges/range_types/null_range.h b/src/include/ranges/nrange.h
similarity index 100%
rename from src/include/ranges/range_types/null_range.h
rename to src/include/ranges/nrange.h
diff --git a/src/include/ranges/subrange.h b/src/include/ranges/prange.h
similarity index 100%
rename from src/include/ranges/subrange.h
rename to src/include/ranges/prange.h
diff --git a/src/include/ranges/single_range.h b/src/include/ranges/urange.h
similarity index 100%
rename from src/include/ranges/single_range.h
rename to src/include/ranges/urange.h