def create_model_resource(resource_map, name, app=Injected):
    """Create a model resource from a dict ``resource_map``
    {'resource name': ('model package', 'model class')}

    :param resource_map: dict with resource descriptions
    :type resource_map: dict(str, tuple(str))
    :param name: name of the concrete resource
    :param app: current application, injected
    :type app: Zsl
    :return: instantiated model resource
    """
    try:
        resource_description = resource_map[name]
        if len(resource_description) == 2:
            module_name, model_name = resource_map[name]
            resource_class = ModelResource
        elif len(resource_description) == 3:
            module_name, model_name, resource_class = resource_map[name]
        else:
            raise ImportError("Invalid resource description for resource '{0}'".format(name))
    except KeyError:
        raise ImportError("Missing resource description for resource '{0}'".format(name))

    module = importlib.import_module(module_name)
    model_cls = getattr(module, model_name)

    return app.injector.create_object(resource_class, {'model_cls': model_cls})