   derivation
  hy1)i have an importer class that do the work of importation.2)the importer is customized with derivation from a base class cBaseImporter for type of mesh:material mesh,textured mesh ,skinned mesh ecc..3)cimportmaterial inherit from cbaseimporter and load material4)the class textured inherit from  cimportmaterial and do textures5)(-the problem-)the skinned mesh can be skinnedtextured or skinnedmaterial and how class i must inherit for have the skinned code only at once?if i inherit from material mesh and insert skin code i must reinsert skin code in skinnedtextured and i i have a bug in the skinned code i must change it 2 times.what advice to me?what is the correct derivation behaviour?Thanks   
  You could use composition:class SkinnedMeshImporter : BaseImporter{private:  SkinnedImporter* skinnedImporter;  MeshImporter* meshImporter;public:  ....};In your import method you analyze the file chunks and import the skinning info using the SkinnedImporter and the mesh using the MeshImporter (provided your format allows you to identify chunk types).   