diff --git a/src/backend-device-factory.cpp b/src/backend-device-factory.cpp
index 857b2bb34a..c05d928df2 100644
--- a/src/backend-device-factory.cpp
+++ b/src/backend-device-factory.cpp
@@ -25,52 +25,25 @@ std::shared_ptr< backend > create_backend();
 }  // namespace librealsense
 
 
-namespace {
-
-
-// Returns true if the left group is completely accounted for in the right group
-//
-bool group_contained_in( librealsense::platform::backend_device_group const & first_data,
-                         librealsense::platform::backend_device_group const & second_data )
-{
-    for( auto && uvc : first_data.uvc_devices )
-    {
-        if( std::find( second_data.uvc_devices.begin(), second_data.uvc_devices.end(), uvc )
-            == second_data.uvc_devices.end() )
-            return false;
-    }
-    for( auto && usb : first_data.usb_devices )
-    {
-        if( std::find( second_data.usb_devices.begin(), second_data.usb_devices.end(), usb )
-            == second_data.usb_devices.end() )
-            return false;
-    }
-    for( auto && hid : first_data.hid_devices )
-    {
-        if( std::find( second_data.hid_devices.begin(), second_data.hid_devices.end(), hid )
-            == second_data.hid_devices.end() )
-            return false;
-    }
-    return true;
-}
+namespace librealsense {
 
 
-std::vector< std::shared_ptr< librealsense::platform::platform_device_info > >
-subtract_sets( const std::vector< std::shared_ptr< librealsense::platform::platform_device_info > > & first,
-               const std::vector< std::shared_ptr< librealsense::platform::platform_device_info > > & second )
+std::vector< std::shared_ptr< platform::platform_device_info > >
+subtract_sets( const std::vector< std::shared_ptr< platform::platform_device_info > > & first,
+               const std::vector< std::shared_ptr< platform::platform_device_info > > & second )
 {
-    std::vector< std::shared_ptr< librealsense::platform::platform_device_info > > results;
+    std::vector< std::shared_ptr< platform::platform_device_info > > results;
     std::for_each(
         first.begin(),
         first.end(),
-        [&]( std::shared_ptr< librealsense::platform::platform_device_info > const & data )
+        [&]( std::shared_ptr< platform::platform_device_info > const & data )
         {
             if( std::find_if(
                     second.begin(),
                     second.end(),
-                    [&]( std::shared_ptr< librealsense::platform::platform_device_info > const & new_dev )
+                    [&]( std::shared_ptr< platform::platform_device_info > const & new_dev )
                     {
-                        return group_contained_in( data->get_group(), new_dev->get_group() );
+                        return data->get_group().is_contained_in( new_dev->get_group() );
                     } )
                 == second.end() )
             {
@@ -81,12 +54,6 @@ subtract_sets( const std::vector< std::shared_ptr< librealsense::platform::platf
 }
 
 
-}  // namespace
-
-
-namespace librealsense {
-
-
 // This singleton creates the actual backend; as long as someone holds it, the backend will stay alive.
 // The instance is held below by the device-watcher. I.e., the device-watcher triggers creation of the
 // backend!
diff --git a/src/platform/backend-device-group.h b/src/platform/backend-device-group.h
index c992f2210b..24a535cf35 100644
--- a/src/platform/backend-device-group.h
+++ b/src/platform/backend-device-group.h
@@ -13,6 +13,7 @@
 #include <functional>
 #include <vector>
 #include <string>
+#include <algorithm>
 
 
 namespace librealsense {
@@ -106,6 +107,32 @@ struct backend_device_group
 
         return s;
     }
+
+
+    // Returns true if this group is completely accounted for in the right group
+    //
+    bool is_contained_in( backend_device_group const & second_data ) const
+    {
+        for( auto & uvc : uvc_devices )
+        {
+            if( std::find( second_data.uvc_devices.begin(), second_data.uvc_devices.end(), uvc )
+                == second_data.uvc_devices.end() )
+                return false;
+        }
+        for( auto & usb : usb_devices )
+        {
+            if( std::find( second_data.usb_devices.begin(), second_data.usb_devices.end(), usb )
+                == second_data.usb_devices.end() )
+                return false;
+        }
+        for( auto & hid : hid_devices )
+        {
+            if( std::find( second_data.hid_devices.begin(), second_data.hid_devices.end(), hid )
+                == second_data.hid_devices.end() )
+                return false;
+        }
+        return true;
+    }
 };
 
 
diff --git a/src/platform/platform-device-info.h b/src/platform/platform-device-info.h
index b22e6e47eb..74254cce5c 100644
--- a/src/platform/platform-device-info.h
+++ b/src/platform/platform-device-info.h
@@ -7,6 +7,7 @@
 #include <src/device-info.h>
 
 #include <memory>
+#include <vector>
 
 
 namespace librealsense {
@@ -59,4 +60,13 @@ class platform_device_info : public device_info
 
 
 }  // namespace platform
+
+
+// subtract_sets( left, right ) = what is in left that's not in right
+//
+std::vector< std::shared_ptr< platform::platform_device_info > >
+subtract_sets( const std::vector< std::shared_ptr< platform::platform_device_info > > & left,
+               const std::vector< std::shared_ptr< platform::platform_device_info > > & right );
+
+
 }  // namespace librealsense