export interface MD_Observer_Interface {
    do_command(from: string, to: string, command: string): void;
}
export interface MD_Observer_Subject_Interface {
    add_observer(observer: MD_Observer_Interface): void;
    notify_all(observer_subject: string, observer_subject_message: string): void;
}
export declare class MD_ObserverSubject {
    protected observers: Array<MD_Observer_Interface>;
    constructor();
    add_observer(observer: MD_Observer_Interface): void;
    notify_all(from: string, to: string, command: string): void;
}