1. NEED TO GO THROUGH A FILTER.
conf(@conid=x1)[
    title(@contitle=x2){functional},
    date(@year=x3,@month=x4,@day=x5){functional},
    paper(@papid=x6)[
        title(@paptitle=x7){functional},
        contact(@conperid=x8){functional},
        author[
            person(@autid=x9)[
                name(@fn2=x10,@ln2=x11){functional},
                email(@email2=x12){functional},
                phone(@phone2=x13){functional}]]]]
:-
ConferencePaper(Y1),Person(Y2),Conference(Y3),
Person(Y4),conference(Y1,Y3),contactPerson(Y1,Y2),
contactPerson(Y1,Y4),pubId(Y1,x6),id(Y2,x8),
number(Y3,x1),eventTitle(Y3,x2),date(Y3,x3),
title(Y1,x7),id(Y4,x9).

2. NEED TO GO THROUGH A FILTER.
conf(@conid=x1)[
    title(@contitle=x2){functional},
    date(@year=x3,@month=x4,@day=x5){functional},
    paper(@papid=x6)[
        title(@paptitle=x7){functional},
        contact(@conperid=x8){functional},
        author[
            person(@autid=x9)[
                name(@fn2=x10,@ln2=x11){functional},
                email(@email2=x12){functional},
                phone(@phone2=x13){functional}]]]]
:-
ConferencePaper(Y1),Person(Y2),Conference(Y3),
Person(Y4),conference(Y1,Y3),contactPerson(Y1,Y2),
author(Y1,Y4),pubId(Y1,x6),id(Y2,x8),
number(Y3,x1),eventTitle(Y3,x2),date(Y3,x3),
title(Y1,x7),id(Y4,x9).