Derive Macro System 

#[derive(System)]
{
    // Attributes available to this derive:
    #[data]
    #[system_type]
    #[process]
    #[aspect]
    #[aspect_a]
    #[aspect_b]
    #[interval]
    #[timed_interval]
    #[activated]
    #[reactivated]
    #[deactivated]
}