diff --git a/EGkGeoObj.h b/EGkGeoObj.h
index 9e7406f..9aeb0b9 100644
--- a/EGkGeoObj.h
+++ b/EGkGeoObj.h
@@ -34,7 +34,7 @@ class _declspec( novtable) IGeoObj
       virtual ~IGeoObj( void) {} 
       virtual IGeoObj* Clone( void) const = 0 ;
       virtual GeoObjType GetType( void) const = 0 ;
-      virtual std::string GetKey( void) const = 0 ;
+      virtual const std::string& GetKey( void) const = 0 ;
       virtual bool IsValid( void) const = 0 ;
       virtual bool Save( std::ostream& osOut) const = 0 ;
       virtual bool Load( CScan& TheScanner) = 0 ;
@@ -48,4 +48,4 @@ class _declspec( novtable) IGeoObj
 } ;
 
 //-----------------------------------------------------------------------------
-EGK_EXPORT IGeoObj* CreateGeoObj( std::string sKey) ;
\ No newline at end of file
+EGK_EXPORT IGeoObj* CreateGeoObj( int nType) ;
\ No newline at end of file
diff --git a/EGkGeoObjType.h b/EGkGeoObjType.h
index a0b925d..1e9ebbe 100644
--- a/EGkGeoObjType.h
+++ b/EGkGeoObjType.h
@@ -28,12 +28,3 @@ enum GeoObjType { GEO_NONE =    0,
                   CRV_BEZ =     ( GEO_CURVE + 2),
                   CRV_COMPO =   ( GEO_CURVE + 3),
                   SRF_TRIMESH = ( GEO_SURF + 0)} ;
-
-//----------------- Costanti chiavi oggetto geometrico ------------------------
-static const char* KEY_GEO_VECT3D  = "G_VEC" ;
-static const char* KEY_GEO_PNT3D   = "G_PNT" ;
-static const char* KEY_CRV_LINE    = "C_LIN" ;
-static const char* KEY_CRV_ARC     = "C_ARC" ;
-static const char* KEY_CRV_BEZ     = "C_BEZ" ;
-static const char* KEY_CRV_COMPO   = "C_CMP" ;
-static const char* KEY_SRF_TRIMESH = "S_TRM" ;
diff --git a/EGkGeoPoint3d.h b/EGkGeoPoint3d.h
index f15cc1d..137bbc3 100644
--- a/EGkGeoPoint3d.h
+++ b/EGkGeoPoint3d.h
@@ -25,7 +25,7 @@ class _declspec( novtable) IGeoPoint3d : public IGeoObj
 
 //-----------------------------------------------------------------------------
 inline IGeoPoint3d* CreateGeoPoint3d( void)
-               { return (static_cast<IGeoPoint3d*>( CreateGeoObj( KEY_GEO_PNT3D))) ; }
+               { return (static_cast<IGeoPoint3d*>( CreateGeoObj( GEO_PNT3D))) ; }
 inline IGeoPoint3d* CloneGeoPoint3d( const IGeoObj* pGObj)
                { if ( pGObj == nullptr  ||  pGObj->GetType() != GEO_PNT3D)
                    return nullptr ;
diff --git a/EGkGeoVector3d.h b/EGkGeoVector3d.h
index db8b338..f5ad8fd 100644
--- a/EGkGeoVector3d.h
+++ b/EGkGeoVector3d.h
@@ -25,7 +25,7 @@ class _declspec( novtable) IGeoVector3d : public IGeoObj
 
 //-----------------------------------------------------------------------------
 inline IGeoVector3d* CreateGeoVector3d( void)
-               { return (static_cast<IGeoVector3d*>( CreateGeoObj( KEY_GEO_VECT3D))) ; }
+               { return (static_cast<IGeoVector3d*>( CreateGeoObj( GEO_VECT3D))) ; }
 inline IGeoVector3d* CloneGeoVector3d( const IGeoObj* pGObj)
                { if ( pGObj == nullptr  ||  pGObj->GetType() != GEO_VECT3D)
                    return nullptr ;
diff --git a/EgkCurveArc.h b/EgkCurveArc.h
index 864411e..147c5c6 100644
--- a/EgkCurveArc.h
+++ b/EgkCurveArc.h
@@ -34,7 +34,7 @@ class _declspec( novtable) ICurveArc : public ICurve
 
 //-----------------------------------------------------------------------------
 inline ICurveArc* CreateCurveArc( void)
-               { return (static_cast<ICurveArc*>( CreateGeoObj( KEY_CRV_ARC))) ; }
+               { return (static_cast<ICurveArc*>( CreateGeoObj( CRV_ARC))) ; }
 inline ICurveArc* CloneCurveArc( const IGeoObj* pGObj)
                { if ( pGObj == nullptr  ||  pGObj->GetType() != CRV_ARC)
                    return nullptr ;
diff --git a/EgkCurveBezier.h b/EgkCurveBezier.h
index 0fcbce7..9646147 100644
--- a/EgkCurveBezier.h
+++ b/EgkCurveBezier.h
@@ -30,7 +30,7 @@ class _declspec( novtable) ICurveBezier : public ICurve
 
 //-----------------------------------------------------------------------------
 inline ICurveBezier* CreateCurveBezier( void)
-               { return (static_cast<ICurveBezier*>( CreateGeoObj( KEY_CRV_BEZ))) ; }
+               { return (static_cast<ICurveBezier*>( CreateGeoObj( CRV_BEZ))) ; }
 inline ICurveBezier* CloneCurveBezier( const IGeoObj* pGObj)
                { if ( pGObj == nullptr  ||  pGObj->GetType() != CRV_BEZ)
                     return nullptr ;
diff --git a/EgkCurveComposite.h b/EgkCurveComposite.h
index 77ed028..5e7cfec 100644
--- a/EgkCurveComposite.h
+++ b/EgkCurveComposite.h
@@ -28,7 +28,7 @@ class _declspec( novtable) ICurveComposite : public ICurve
 
 //-----------------------------------------------------------------------------
 inline ICurveComposite* CreateCurveComposite( void)
-               { return (static_cast<ICurveComposite*>( CreateGeoObj( KEY_CRV_COMPO))) ; }
+               { return (static_cast<ICurveComposite*>( CreateGeoObj( CRV_COMPO))) ; }
 inline ICurveComposite* CloneCurveComposite( const IGeoObj* pGObj)
                { if ( pGObj == nullptr  ||  pGObj->GetType() != CRV_COMPO)
                     return nullptr ;
diff --git a/EgkCurveLine.h b/EgkCurveLine.h
index e4ff346..63010d2 100644
--- a/EgkCurveLine.h
+++ b/EgkCurveLine.h
@@ -26,7 +26,7 @@ class _declspec( novtable) ICurveLine : public ICurve
 
 //-----------------------------------------------------------------------------
 inline ICurveLine* CreateCurveLine( void)
-               { return (static_cast<ICurveLine*>( CreateGeoObj( KEY_CRV_LINE))) ; }
+               { return (static_cast<ICurveLine*>( CreateGeoObj( CRV_LINE))) ; }
 inline ICurveLine* CloneCurveLine( const IGeoObj* pGObj)
                { if ( pGObj == nullptr  ||  pGObj->GetType() != CRV_LINE)
                    return nullptr ;