Index: objects/object_calcer.h
===================================================================
--- objects/object_calcer.h
+++ objects/object_calcer.h
@@ -78,12 +78,14 @@
   void ref();
   void deref();
 
+  std::vector<ObjectCalcer*> mparents;
+
   // we keep track of our children, so algorithms can easily walk over
   // the dependency graph..
-
   std::vector<ObjectCalcer*> mchildren;
 
   ObjectCalcer();
+  ObjectCalcer( const std::vector<ObjectCalcer*>& parents );
 public:
   /**
    * a calcer should call this to register itself as a child of this
@@ -103,13 +105,13 @@
   /**
    * Returns the child ObjectCalcer's of this ObjectCalcer.
    */
- std::vector<ObjectCalcer*> children() const;
+  const std::vector<ObjectCalcer*>& children() const;
 
   virtual ~ObjectCalcer();
   /**
    * Returns the parent ObjectCalcer's of this ObjectCalcer.
    */
-  virtual std::vector<ObjectCalcer*> parents() const = 0;
+  const virtual std::vector<ObjectCalcer*>& parents() const;
   /**
    * Returns the ObjectImp of this ObjectCalcer.
    */
@@ -183,7 +185,6 @@
 class ObjectTypeCalcer
   : public ObjectCalcer
 {
-  std::vector<ObjectCalcer*> mparents;
   const ObjectType* mtype;
   ObjectImp* mimp;
 public:
@@ -200,7 +201,6 @@
   ~ObjectTypeCalcer();
 
   const ObjectImp* imp() const Q_DECL_OVERRIDE;
-  std::vector<ObjectCalcer*> parents() const Q_DECL_OVERRIDE;
   void calc( const KigDocument& doc ) Q_DECL_OVERRIDE;
 
   /**
@@ -249,7 +249,6 @@
 
   const ObjectImp* imp() const Q_DECL_OVERRIDE;
   void calc( const KigDocument& doc ) Q_DECL_OVERRIDE;
-  std::vector<ObjectCalcer*> parents() const Q_DECL_OVERRIDE;
 
   /**
    * Set the ObjectImp of this ObjectConstCalcer to the given
@@ -277,7 +276,6 @@
   : public ObjectCalcer
 {
   ObjectImp* mimp;
-  ObjectCalcer* mparent;
   int mpropgid;
 /*
  * The following two variables are used for a caching
@@ -305,7 +303,6 @@
   ~ObjectPropertyCalcer();
 
   const ObjectImp* imp() const Q_DECL_OVERRIDE;
-  std::vector<ObjectCalcer*> parents() const Q_DECL_OVERRIDE;
   void calc( const KigDocument& doc ) Q_DECL_OVERRIDE;
 
   ObjectCalcer* parent() const;
Index: objects/object_calcer.cc
===================================================================
--- objects/object_calcer.cc
+++ objects/object_calcer.cc
@@ -42,8 +42,13 @@
 
 ObjectTypeCalcer::ObjectTypeCalcer( const ObjectType* type, 
       const std::vector<ObjectCalcer*>& parents, bool sort )
-  : mparents( ( sort )?type->sortArgs( parents ):parents ), mtype( type ), mimp( 0 )
+  : ObjectCalcer( parents ), mtype( type ), mimp( 0 )
 {
+  if ( sort )
+  {
+    mparents = type->sortArgs( mparents );
+  }
+
   std::for_each( mparents.begin(), mparents.end(),
                  std::bind2nd( std::mem_fun( &ObjectCalcer::addChild ), this ) );
 }
@@ -71,12 +76,6 @@
 {
 }
 
-std::vector<ObjectCalcer*> ObjectConstCalcer::parents() const
-{
-  // we have no parents..
-  return std::vector<ObjectCalcer*>();
-}
-
 void ObjectCalcer::ref()
 {
   ++refcount;
@@ -102,11 +101,6 @@
   return mimp;
 }
 
-std::vector<ObjectCalcer*> ObjectTypeCalcer::parents() const
-{
-  return mparents;
-}
-
 void ObjectCalcer::addChild( ObjectCalcer* c )
 {
   mchildren.push_back( c );
@@ -135,16 +129,17 @@
 }
 
 ObjectPropertyCalcer::ObjectPropertyCalcer( ObjectCalcer* parent, const char* pname )
-  : mimp( 0 ), mparent( parent ), mparenttype( 0 )
+  : mimp( 0 ), mparenttype( 0 )
 {
-  mparent->addChild( this );
-  mpropgid = mparent->imp()->getPropGid( pname );
+  mparents.push_back( parent );
+  mparents.front()->addChild( this );
+  mpropgid = mparents.front()->imp()->getPropGid( pname );
 }
 
 ObjectPropertyCalcer::ObjectPropertyCalcer( ObjectCalcer* parent, int propid, bool islocal )
-  : mimp( 0 ), mparent( parent ), mparenttype( 0 )
+  : mimp( 0 ), mparenttype( 0 )
 {
-  mparent->addChild( this );
+  mparents.front()->addChild( this );
   if ( islocal )
   {
     mpropgid = parent->imp()->getPropGid( parent->imp()->propertiesInternalNames()[propid] );
@@ -155,36 +150,30 @@
 
 ObjectPropertyCalcer::~ObjectPropertyCalcer()
 {
-  mparent->delChild( this );
+  mparents.front()->delChild( this );
   delete mimp;
 }
 
 const ObjectImp* ObjectPropertyCalcer::imp() const
 {
   return mimp;
 }
 
-std::vector<ObjectCalcer*> ObjectPropertyCalcer::parents() const
-{
-  std::vector<ObjectCalcer*> ret;
-  ret.push_back( mparent );
-  return ret;
-}
-
 void ObjectPropertyCalcer::calc( const KigDocument& doc )
 {
+  const ObjectCalcer* sole_parent = mparents.front();
   //if ( mparenttype != mparent->imp()->type() )
-  if ( mparenttype == 0 || *mparenttype != typeid( *(mparent->imp()) ) )
+  if ( mparenttype == 0 || *mparenttype != typeid( *( sole_parent->imp() ) ) )
   {
-    mpropid = mparent->imp()->getPropLid( mpropgid );
+    mpropid = sole_parent->imp()->getPropLid( mpropgid );
 //    mparenttype = mparent->imp()->type();
-    mparenttype = &typeid( *(mparent->imp()) );
+    mparenttype = &typeid( *( sole_parent->imp() ) );
 //    printf ("changing type, new type: %s\n", mparenttype->internalName());
   }
   ObjectImp* n;
   if ( mpropid >= 0 )
   {
-    n = mparent->imp()->property( mpropid, doc );
+    n = sole_parent->imp()->property( mpropid, doc );
   } else n = new InvalidImp;
   delete mimp;
   mimp = n;
@@ -197,16 +186,21 @@
   return ret;
 }
 
-std::vector<ObjectCalcer*> ObjectCalcer::children() const
+const std::vector<ObjectCalcer*>& ObjectCalcer::children() const
 {
   return mchildren;
 }
 
+const std::vector<ObjectCalcer*>& ObjectCalcer::parents() const
+{
+  return mparents;
+}
+
 const ObjectImpType* ObjectPropertyCalcer::impRequirement(
   ObjectCalcer*, const std::vector<ObjectCalcer*>& ) const
 {
-  int proplid = mparent->imp()->getPropLid( mpropgid );
-  return mparent->imp()->impRequirementForProperty( proplid );
+  int proplid = mparents.front()->imp()->getPropLid( mpropgid );
+  return mparents.front()->imp()->impRequirementForProperty( proplid );
 }
 
 const ObjectImpType* ObjectConstCalcer::impRequirement(
@@ -296,11 +290,16 @@
 
 ObjectCalcer* ObjectPropertyCalcer::parent() const
 {
-  return mparent;
+  return mparents.front();
 }
 
 ObjectCalcer::ObjectCalcer()
-  : refcount( 0 )
+  : refcount( 0 ),  mparents( 0 )
+{
+}
+
+ObjectCalcer::ObjectCalcer( const std::vector<ObjectCalcer*>& parents )
+  : refcount( 0 ),  mparents( parents )
 {
 }
 
@@ -321,9 +320,9 @@
 
 bool ObjectPropertyCalcer::isDefinedOnOrThrough( const ObjectCalcer* o ) const
 {
-  return o == mparent &&
-    mparent->imp()->isPropertyDefinedOnOrThroughThisImp( 
-       mparent->imp()->getPropLid( mpropgid ) );
+  return o == mparents.front() &&
+         mparents.front()->imp()->isPropertyDefinedOnOrThroughThisImp(
+           mparents.front()->imp()->getPropLid( mpropgid ) );
 }
 
 bool ObjectTypeCalcer::isDefinedOnOrThrough( const ObjectCalcer* o ) const
@@ -342,7 +341,7 @@
 
 int ObjectPropertyCalcer::propLid() const
 {
-  return mparent->imp()->getPropLid( mpropgid );
+  return mparents.front()->imp()->getPropLid( mpropgid );
 }
 
 int ObjectPropertyCalcer::propGid() const