rule createSystem
    transform s : XAmm!XARepo
    to o: GENmm!GSystem {
        o.name = s.libname(); // a custom operation not in listing
        o.packages = s.libraries.equivalent();
        o.userMessages = s.messageDetails.equivalent();
}

// this rule work as expected.
rule transformMessageDetail
    transform i: XAmm!XAMessageDetail
    to userMessage: GENmm!GUserMessage {
            userMessage.key = i.msgId;
            userMessage.text = i.text;
}
 
// library are not transform.   
rule transformLibrary
    transform i: XAmm!ILibrary
    to  userMessage: GENmm!GPackage {

}

o.packages = s.libraries.equivalent();
o.userMessages = s.messageDetails.equivalent();