template<typename Component, typename Tag = default_tag> 
class component_t {
public:
  // construct/copy/destruct
  component_t();
  template<typename T0> component_t(const T0 &);
  template<typename T0> component_t(T0 &);
  component_t(const component_t &);

  // public member functions
  void invoke() ;
  bool is_invocable() ;
  size_t num_ports() const;
  port & get_port(int) ;
  std::auto_ptr< component > copy() const;
  Component & get() ;
  runtime_base_class_type * get_pointer() ;

  // private member functions
  void component_t_() ;
};