class Backend;
class BackendSet;
typedef boost::shared_ptr<Backend> BackendPtr;
typedef boost::shared_ptr<Frontend> FrontendPtr;
typedef boost::shared_ptr<Package> PackagePtr;
class Backend;
class BackendSet;
typedef boost::shared_ptr<Backend> BackendPtr;
typedef boost::shared_ptr<Frontend> FrontendPtr;
typedef boost::shared_ptr<Package> PackagePtr;