public void generateAmpString () {
        ampString = "(" + performative;
        if (!sender.equals(""))
            ampString = ampString + "\n  :SENDER " + sender;
        if (!receiver.equals(""))
            ampString = ampString + "\n  :RECEIVER " + receiver;
        if (!replyWith.equals(""))
            ampString = ampString + "\n  :REPLY-WITH " + replyWith;
        if (!inReplyTo.equals(""))
            ampString = ampString + "\n  :IN-REPLY-TO " + inReplyTo;
        if (!content.equals(""))
            ampString = ampString + "\n  :CONTENT " + content;
        if (!language.equals(""))
            ampString = ampString + "\n  :LANGUAGE " + language;
        if (!ontology.equals(""))
            ampString = ampString + "\n  :ONTOLOGY " + ontology;
        if (!force.equals(""))
            ampString = ampString + "\n  :FORCE " + force;
        ampString = ampString + ")";
    }